all the students in the 6th grade either purchased their lunch or brought their lunch from home on monday.how many students are in the sixth grade if

The probability that 4 or more students score 85 percent or higher on the exam is 0.1209 or approximately 12.09 percent.

To solve this problem, we need to use the binomial distribution formula. We know that the probability of each student scoring 85 percent or higher on the exam is p = 0.2 (since 20 percent is equivalent to 85 percent or higher). We also know that n = 10 students took the exam.

Now we need to find the probability that 4 or more students score 85 percent or higher. We can use the binomial probability formula to calculate this:

P(X ≥ 4) = 1 - P(X < 4)

= 1 - (P(X = 0) + P(X = 1) + P(X = 2) + P(X = 3))

= [tex]1 - [(10 choose 0) * 0.2^0 * (0.8)^10 + (10 choose 1) * 0.2^1 * (0.8)^9 + (10 choose 2) * 0.2^2 * (0.8)^8 + (10 choose 3) * 0.2^3 * (0.8)^7][/tex]
= 1 - (0.1074 + 0.2684 + 0.3020 + 0.2013)

= 0.1209

Therefore, the probability that 4 or more students score 85 percent or higher on the exam is 0.1209 or approximately 12.09 percent.

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Answer:

9749

Step-by-step explanation:

45000·(1+4%)5-45000

9749.38061

rounded to the nearest penny

9749

The differential of the function z = x^6 ln(y^4) is dz = 6x^5 ln(y^4) dx + 4x^6 (1/y) dy.

To find the differential of the function z = x^6 ln(y^4), we use the rules of partial differentiation.

Taking the partial derivative of z with respect to x, we get ∂z/∂x = 6x^5 ln(y^4).

Taking the partial derivative of z with respect to y, we get ∂z/∂y = (4x^6/y) ln(y^4).

Then, using the differential notation, we can write dz = (∂z/∂x) dx + (∂z/∂y) dy.

Substituting the values we calculated for ∂z/∂x and ∂z/∂y, we get dz = 6x^5 ln(y^4) dx + 4x^6 (1/y) dy.

This represents the differential of the function z = x^6 ln(y^4).

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If x = x1(t) and y = y1(t) and x = x2(t) and y = y2(t) are any two solutions of the linear nonhomogeneous system given by x' = p11(t)x + p12(t)y + g1(t), y' = p21(t)x + p22(t)y + g2(t), then x = x1(t) - x2(t) and y = y1(t) - y2(t) is a solution of the corresponding homogeneous system given by x' = p11(t)x + p12(t)y, y' = p21(t)x + p22(t)y.

To show that x = x1(t) - x2(t) and y = y1(t) - y2(t) is a solution of the corresponding homogeneous system, we need to verify that it satisfies the differential equations x' = p11(t)x + p12(t)y and y' = p21(t)x + p22(t)y with g1(t) = g2(t) = 0. Using the properties of derivatives, we can calculate that x' = x1'(t) - x2'(t) and y' = y1'(t) - y2'(t). Substituting these expressions and the expressions for x and y into the differential equations, we get:

x' = p11(t)x + p12(t)y

==> x1'(t) - x2'(t) = p11(t)(x1(t) - x2(t)) + p12(t)(y1(t) - y2(t))

==> p11(t)x1(t) + p12(t)y1(t) = p11(t)x2(t) + p12(t)y2(t)

y' = p21(t)x + p22(t)y

==> y1'(t) - y2'(t) = p21(t)(x1(t) - x2(t)) + p22(t)(y1(t) - y2(t))

==> p21(t)x1(t) + p22(t)y1(t) = p21(t)x2(t) + p22(t)y2(t)

Since x1(t), y1(t), x2(t), and y2(t) all satisfy the original nonhomogeneous system, we know that the expressions on the right-hand sides of the above equations are equal to g1(t) and g2(t), which are both zero in the corresponding homogeneous system. Therefore, x = x1(t) - x2(t) and y = y1(t) - y2(t) satisfy the differential equations x' = p11(t)x + p12(t)y and y' = p21(t)x + p22(t)y with g1(t) = g2(t) = 0, and hence they are a solution of the corresponding homogeneous system.

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The equation of the tangent line:

y = (-x - sqrt(2)/2) - (π/2)(x - sqrt(2)/2)

To find the equation of the line tangent to the curve at the point corresponding to t = π/4, we need to find the first derivatives of x and y with respect to t, evaluate them at t = π/4, and then use these values to find the slope of the tangent line.

The first derivative of x with respect to t is:

dx/dt = -sint + tcost

The first derivative of y with respect to t is:

dy/dt = cost + tsint

Evaluating these at t = π/4, we get:

dx/dt|t=π/4 = -sqrt(2)/2

dy/dt|t=π/4 = (sqrt(2)/2) + (π/4)(sqrt(2)/2)

The slope of the tangent line is the ratio of the change in y to the change in x. So, the slope of the tangent line at t = π/4 is:

m = dy/dt|t=π/4 / dx/dt|t=π/4 = -1 - π/2

Now, we can use the point-slope form of the equation of a line to find the equation of the tangent line. Using the point (x(π/4), y(π/4)) = (sqrt(2)/2, sqrt(2)/2), we get:

y - (sqrt(2)/2) = (m)(x - sqrt(2)/2)

Substituting the value of m, we get:

y - (sqrt(2)/2) = (-1 - π/2)(x - sqrt(2)/2)

Expanding and simplifying, we get the equation of the tangent line:

y = (-x - sqrt(2)/2) - (π/2)(x - sqrt(2)/2)

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A random variable is a numerical outcome that is generated by a probability experiment. It is a function that assigns a unique numerical value to each outcome of the experiment.

Random variables can be either discrete or continuous. Discrete random variables take on a countable number of distinct values, while continuous random variables can take on any value within a specified range. In statistical analysis, random variables are used to model the behavior of a system or population of interest. They are often used to describe the distribution of a population or the probability of different outcomes occurring in a given scenario. Random variables are an essential tool in probability theory, statistics, and other areas of mathematics and science.

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To draw a line and measure it to the nearest quarter inch, you will need a ruler or tape measure marked in inches.

Place the ruler or tape measure at one end of the line and align it so that the 0 mark lines up with the beginning of the line. Then, count the number of quarter inches to the end of the line and record the measurement.

Measuring to the nearest quarter inch means that you are rounding the measurement to the nearest multiple of 0.25 inches. For example, if the line measures between 3 and 3.24 inches, it would be rounded down to 3 inches; if it measures between 3.25 and 3.49 inches, it would be rounded up to 3.5 inches. This level of precision is commonly used in construction, woodworking, and other fields where precise measurements are important.

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To determine the number of passes required to sort the elements using insertion sort, we need to first understand how insertion sort works. It involves comparing each element with the previous elements in the list and inserting it into the correct position.

So for this particular list of elements: 14, 12, 16, 6, 3, 10, we can see that the first pass would involve comparing the second element (12) with the first element (14) and swapping them to get: 12, 14, 16, 6, 3, 10.

The second pass would involve comparing the third element (16) with the second element (14) and leaving it in place, then comparing it with the first element (12) and swapping them to get: 12, 14, 16, 6, 3, 10.

Similarly, the third pass would involve comparing the fourth element (6) with the previous elements and inserting it into the correct position, resulting in: 6, 12, 14, 16, 3, 10.

The fourth pass would involve comparing the fifth element (3) with the previous elements and inserting it into the correct position, resulting in: 3, 6, 12, 14, 16, 10.

Finally, the fifth pass would involve comparing the sixth element (10) with the previous elements and inserting it into the correct position, resulting in the fully sorted list: 3, 6, 10, 12, 14, 16.

Therefore, the answer to this question would be 5, which is one of the answer choices given.

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The p-value for the given t-statistic falls between 0.005 and 0.01.

o find the p-value for the given t statistic of -2.63 with degrees of freedom of 24, we need to consult the t-distribution table or use statistical software.

Since the alternative hypothesis is μ < 100, we are conducting a one-tailed test in the left tail of the t-distribution. We want to find the area under the t-distribution curve to the left of -2.63.

Using the t-distribution table or software, we can determine that the p-value falls between 0.005 and 0.01. This means that the p-value for the statistic falls between 0.005 and 0.01.

Therefore, the p-value for the given t-statistic falls between 0.005 and 0.01.

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The expression that is equivalent to (2x² + 7x - 15)/(3x² + 16x + 5) * (3x² - 2x - 1)/(2x² - x - 3) is (D) (x - 1)/(x + 1)

From the question, we have the following parameters that can be used in our computation:

(2x² + 7x - 15)/(3x² + 16x + 5) * (3x² - 2x - 1)/(2x² - x - 3)

When the expressions are factored, we have:

(2x² + 7x - 15)/(3x² + 16x + 5) * (3x² - 2x - 1)/(2x² - x - 3) = (2x - 3)(x + 5)/(3x + 1)(x + 5) * (3x + 1)(x - 1)/(x + 1)(2x - 3)

Cancelling out the common factors, we have

(2x² + 7x - 15)/(3x² + 16x + 5) * (3x² - 2x - 1)/(2x² - x - 3) = (x - 1)/(x + 1)

This means that the equivalent expression is (D) (x - 1)/(x + 1)

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The perimeter of the triangle is 170 inches.

To solve for the perimeter, we first need to find the length of the perpendicular height. We can do this using the sine function:

sin(35°) = 46/x

x = 46/sin(35°) = 65 inches

Now that we know the length of the perpendicular height, we can find the length of the base of the triangle using the cosine function:

cos(35°) = 65/x

x = 65/cos(35°) = 75 inches

The perimeter of the triangle is the sum of the lengths of the three sides, so the perimeter is:

P = 65 + 75 + 30

= 170 inches

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Answer: To compare the final amounts, we need to calculate the compound interest for Brianna and the simple interest for Audra.

For compound interest, the formula to calculate the future value is:

A = P(1 + r/n)^(nt)

Where:

A = the future value/amount

P = the principal amount (initial investment)

r = the annual interest rate (as a decimal)

n = the number of times that interest is compounded per year

t = the number of years

For Brianna:

P = $16,500

r = 8% = 0.08

n = 1 (compounded annually)

t = 13 years

A = 16500(1 + 0.08/1)^(1*13)

A = 16500(1.08)^13

A ≈ $42,159.84

After 13 years, Brianna will have approximately $42,159.84.

For simple interest, the formula to calculate the future value is:

A = P(1 + rt)

Where:

A = the future value/amount

P = the principal amount (initial investment)

r = the annual interest rate (as a decimal)

t = the number of years

For Audra:

P = $16,500

r = 8% = 0.08

t = 13 years

A = 16500(1 + 0.08*13)

A = 16500(1 + 1.04)

A ≈ $39,720

After 13 years, Audra will have approximately $39,720.

To determine who will have more and by how much, we subtract Audra's amount from Brianna's amount:

Difference = Brianna's amount - Audra's amount

Difference = $42,159.84 - $39,720

Difference ≈ $2,439.84

Therefore, at the end of 13 years, Brianna will have approximately $2,439.84 more than Audra.

Step-by-step explanation: :)

Answer:

Brianna will have approximately $2,439.84 more than Audra.

hope it helps u

Step-by-step explanation:

The probability that a random sample of 20 pies will have a mean baking time that exceeds 48 minutes is approximately 0.0037 or 0.37%

We can use the central limit theorem to approximate the distribution of the sample mean baking time. Since the sample size is large enough (20 pies) and the population standard deviation is known, we can use the normal distribution to approximate the distribution of the sample mean.

The mean of the sample mean baking time is the same as the population mean, which is 45 minutes.

To find the probability that a random sample of 20 pies will have a mean baking time that exceeds 48 minutes, we can standardize the sample mean using the formula:

[tex]z=\frac{\bar{x}-\mu}{\frac{\sigma}{\sqrt{n} } }[/tex]

= (48-45)/(5/√20)

= 2.68

Using a standard normal distribution table or calculator, we can find that the probability of a standard normal random variable being greater than 2.68 is approximately 0.0037. Therefore, the probability that a random sample of 20 pies will have a mean baking time that exceeds 48 minutes is approximately 0.0037 or 0.37%

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The minimum order of the Taylor polynomial centred at O for cos x required to approximate cos (-0.85) with an absolute error no greater than 10-4 is 5.

The Taylor series for cos x centred at O is given by:

cos x = 1 - x^2/2! + x^4/4! - x^6/6! + ...

The nth-order Taylor polynomial for cos x centred at O is given by the first n terms of the Taylor series. We want to find the minimum n such that the absolute error between cos (-0.85) and the nth-order Taylor polynomial is no greater than 10-4.

The error term for the nth-order Taylor polynomial is given by:

Rn(x) = cos (c) * xn+1 / (n+1)!

where c is some value between 0 and x.

To find the minimum n, we need to find the value of n such that the error term is no greater than 10-4 for x = -0.85.

Substituting x = -0.85 into the error term and using the fact that |cos (c)| <= 1, we have:

|Rn(-0.85)| <= |(-0.85)^(n+1) / (n+1)!|

We want to find the minimum n such that the right-hand side is no greater than 10-4.

We can use a computer or calculator to find that n = 5 is the smallest integer that satisfies this condition. Therefore, the minimum order of the Taylor polynomial centred at O for cos x required to approximate cos (-0.85) with an absolute error no greater than 10-4 is 5.

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The cooling rate of the turkey is 0.45°F per minute. This means that every minute, the temperature of the turkey decreases by 0.45°F.

The cooling rate of a roasted turkey can be determined by the rate at which it loses heat to its surroundings. In this case, the temperature of the turkey was 191°F when it was taken out of the oven and placed on a table in a room with a temperature of 75°F. After half an hour, the temperature of the turkey had decreased to 155°F.

To calculate the cooling rate, we can use Newton's law of cooling, which states that the rate of heat loss of an object is proportional to the difference in temperature between the object and its surroundings. The equation for Newton's law of cooling is:

dT/dt = -k (T - Ts)

where dT/dt is the rate of change of temperature with respect to time, T is the temperature of the turkey at time t, Ts is the temperature of the surroundings (75°F), and k is a constant that depends on the specific heat of the turkey, its surface area, and other factors.

To solve for k, we can use the data given:

dT/dt = -k (T - Ts)

-36 = -k (155 - 75)

-36 = -k (80)

k = 0.45

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After considering all the data we conclude that the area of the region enclosed by the astroid is (3/8) π a⁴, under the condition that  x = a cos3θ, y = a sin3θ.

The astroid curve is given by x = a cos³θ, y = a sin³θ. The area enclosed by the astroid curve is given by the integral of ½ y dx from θ = 0 to θ = 2π ².

Staging x = a cos³θ and y = a sin³θ in ½ y dx, we get:

½ y dx = ½ a sin³θ (−3a sin²θ dθ) = −3/2 a⁴ cos⁶θ sin⁴θ dθ

Applying Integration to this expression from θ = 0 to θ = 2π provides us the area enclosed by the astroid curve:

A = ∫₀²π −3/2 a⁴ cos⁶θ sin⁴θ dθ

A = (3/8) π a⁴

Therefore, the area enclosed by the astroid curve is (3/8) π a⁴.
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The integral of sin^4(8q)cos(8q) with respect to q is (1/40)sin^5(8q) + C or (3/8)cos(32q) - (1/64)cos(16q) + C, where C is the constant of integration.

Using the product-to-sum identity for cosine, we can rewrite the integrand as sin(2x+2x+2x+2x)cos(2x+2x) = [sin(2x+2x)cos(2x+2x) + sin(2x)cos(2x+2x+2x)]cos(2x+2x).

We can then use the double angle formula for sine and cosine to simplify the integrand to (3/8)sin(16x) - (1/8)sin(8x) + C. Therefore, the integral of sin4(8q)cos(8q) is (3/8)cos(16q) - (1/64)cos(8q) + C.

To evaluate the integral ∫sin4(8q)cos(8q)dq, we start by using the product-to-sum identity for cosine:

cos(a)sin(b) = 1/2[sin(a+b) + sin(a-b)]

We can rewrite the integrand as:

sin(8q)cos(8q)sin(8q)cos(8q) = [sin(8q+8q)cos(8q+8q) + sin(8q)cos(8q+8q+8q)]cos(8q+8q)

Using the double angle formula for sine and cosine, we can simplify the first term as:

sin(16q)cos(16q) = (1/2)sin(2*16q) = (1/2)sin(32q)

For the second term, we can apply the product-to-sum identity for sine:

sin(a)cos(b) = 1/2[sin(a+b) - sin(a-b)]

sin(8q)cos(8q+8q+8q) = 1/2[sin(8q+24q) - sin(8q-16q)] = 1/2[sin(32q) + sin(8q)]

Putting everything together, we have:

∫sin4(8q)cos(8q)dq = ∫[sin(16q)/2 + sin(32q)/2 + sin(8q)/2]cos(16q)dq

Using the substitution u = 16q, we have:

(1/16)∫[sin(u)/2 + sin(2u)/2 + sin(u/2)/2]cos(u)du

We can then integrate each term separately:

∫sin(u)cos(u)du = (1/2)sin^2(u) + C1

∫sin(2u)cos(u)du = (1/2)[(1/2)sin(3u)] + C2

∫sin(u/2)cos(u)du = -2cos(u/2) + C3

Substituting back, we get:

(1/16)[(1/2)sin^2(16q) + (1/4)sin^2(32q) - 2cos(8q) + C4]

Simplifying, we get:

(3/8)sin^2(16q) - (1/8)sin^2(8q) + C5

Using the identity sin^2(x) = (1-cos(2x))/2, we can rewrite this as:

(3/8)(1-cos(32q))/2 - (1/8)(1-cos(16q))/2 + C6

= (3/8)

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The length of the hypotenuse of this triangle is approximately 15.03 inches (rounded to the nearest tenth).

To find the length of the hypotenuse in a right triangle, we can use the trigonometric function cosine.

Given:

Leg length (adjacent side) = 7 in

Angle opposite the leg = 62°

We can use the cosine function, which relates the adjacent side and the hypotenuse of a right triangle:

cos(angle) = adjacent/hypotenuse

Let's substitute the known values into the equation:

cos(62°) = 7/hypotenuse

To solve for the hypotenuse, we rearrange the equation:

hypotenuse = 7/cos(62°)

Using a calculator, we find:

cos(62°) ≈ 0.4663

Now we can substitute this value into the equation:

hypotenuse = 7/0.4663

Calculating this, we get:

hypotenuse ≈ 15.03

Therefore, the length of the hypotenuse of this triangle is approximately 15.03 inches (rounded to the nearest tenth).

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Thus, we can find nonzero matrices a, b, and c such that ac = bc and a is not equal to b by using the distributive property of matrix multiplication. One example of such matrices is provided above.

The problem statement requires us to find three matrices - a, b, and c, such that their product ac is equal to bc but a is not equal to b. To solve this problem, we need to use the properties of matrix multiplication. One such property is the distributive property, which states that a(b + c) = ab + ac, where a, b, and c are matrices.

Let's assume that a, b, and c are all 2x2 matrices. One example of such matrices could be:

a = [1 0]
   [0 2]

b = [2 0]
   [0 1]

c = [1 2]
   [3 4]

Using these matrices, we can verify that ac = bc, as follows:

ac = [1 0]  [1 2] = [1 2]
    [0 2]  [3 4]   [6 8]

bc = [2 0]  [1 2] = [2 4]
    [0 1]  [3 4]   [3 4]

As we can see, both products result in the same matrix. However, a and b are not equal, as a(1,1) = 1 and b(1,1) = 2. Therefore, we have found an example of three nonzero matrices such that ac = bc but a is not equal to b.

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The correlation coefficient between x and y is 0.61. The formula for the correlation coefficient (r) between two variables x and y is:

r = covariance(x, y) / (standard deviation(x) * standard deviation(y))

We are given that the covariance between x and y is 1225, the variance of x is 1600, and the variance of y is 2500. Since variance is the square of standard deviation, we can calculate the standard deviations of x and y as:

standard deviation(x) = sqrt(variance(x)) = √(1600) = 40

standard deviation(y) = sqrt(variance(y)) = √(2500) = 50

Plugging in these values into the formula for the correlation coefficient, we get:

r = 1225 / (40 * 50) = 0.61

r = 1225/(2000) = 0.61

Therefore, the correlation coefficient between x and y is 0.61.

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The given order of integration is dx first, then dy, and finally dz. To change the order of integration to dz first, then dx, and finally dy, we need to identify the new limits of integration. We can do this by using the given limits of integration and setting up the new integrals. The equivalent integral with the new order of integration is ∫0^1 ∫0^2x ∫0^20 f(x,y,z)dzdxdy.

To change the order of integration, we need to identify the new limits of integration. We can do this by looking at the given limits of integration and setting up the new integrals. First, we need to integrate with respect to z, so we set the limits of integration for z from 0 to 1 - 2x.

Next, we integrate with respect to x, so we set the limits of integration for x from 0 to 2y. Finally, we integrate with respect to y, so we set the limits of integration for y from 0 to 1/4.

Putting it all together, we get the equivalent integral with the new order of integration: ∫0^1 ∫0^2x ∫0^20 f(x,y,z)dzdxdy.

To change the order of integration, we need to identify the new limits of integration. We can do this by setting up the new integrals based on the given limits of integration. The equivalent integral with the new order of integration is ∫0^1 ∫0^2x ∫0^20 f(x,y,z)dzdxdy.

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Answer:

it will take 9 hours to empty the pool.

Step-by-step explanation:

Answer:

X= 95 Y=55

Step-by-step explanation:

95X5= 475

2X55= 110

475+110= 585

I hope this helps! : )

The first partial derivatives with respect to x, y, and z of the given function f(x, y, z) = 2x^2y − 9xyz/10yz^2 are:

fx = 4xy - (9yz/10z^2) = 4xy - (9/10z)

fy = 2x^2 - (9xz/10z^2) = 2x^2 - (9x/10z)

fz = (-9xy/5yz^2) - (18xyz/5yz^3) = (-9x/5z) - (18x/5y)

The partial derivative of a multivariable function with respect to a particular variable is calculated by considering all other variables as constants and differentiating with respect to the chosen variable. In this case, the partial derivative with respect to x involves differentiating the function with respect to x while treating y and z as constants, and similarly for y and z. The obtained partial derivatives are then used to find critical points, which are the points where all partial derivatives are zero.

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Therefore, The most general antiderivative of the function g(x) = cos(x) - 8sin(x) is F(x) = sin(x) + 8cos(x) + C. We can check the answer by differentiating F(x) which will give us g(x) = cos(x) - 8sin(x).

The most general antiderivative of the function g(x) = cos(x) - 8sin(x) is F(x) = sin(x) + 8cos(x) + C, where C is the constant of integration.
Explanation: To find the antiderivative of g(x), we use the formulae of integration of trigonometric functions. ∫cos(x) dx = sin(x) + C and ∫sin(x) dx = -cos(x) + C. Therefore, ∫cos(x) − 8sin(x) dx = ∫cos(x) dx − 8∫sin(x) dx = sin(x) + 8cos(x) + C. To check our answer, we differentiate F(x) with respect to x, we get g(x) = cos(x) - 8sin(x).

Therefore, The most general antiderivative of the function g(x) = cos(x) - 8sin(x) is F(x) = sin(x) + 8cos(x) + C. We can check the answer by differentiating F(x) which will give us g(x) = cos(x) - 8sin(x).

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Here, the outer sum is over the variable $i$ and it ranges from $1$ to $n$. For each value of $i$, the inner sum is over the variable $j$ and it ranges from $1$ to $3$.

The expression $j^2$ is the summand, which is added for each value of $j$.

The given sigma notation is:

n

___

\    j^2

/___

j=1

Expanding this sigma notation, we have:

= 1^2 + 2^2 + 3^2 + ... + (n-1)^2 + n^2

= (1 + 4 + 9 + ... + (n-1)^2) + n^2

The sum of squares up to n-1 can be expressed using the formula:

1^2 + 2^2 + 3^2 + ... + (n-1)^2 = n(n-1)(2n-1)/6

Substituting this in the above expression, we get:

= n(n-1)(2n-1)/6 + n^2

= (2n^3 - 3n^2 + n)/6

Therefore, the expanded form of the given sigma notation is (2n^3 - 3n^2 + n)/6.

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There are 96 different possible combos.

The principle used to calculate the number of possible combos is called the multiplication principle.

We have,

(a)

The number of possible combos, when you select a popcorn, a candy, and a soda.

= 8 (choices of candy) x 6 (choices of soda) x 2 (choices of popcorn)

= 96

(b)

The principle used to calculate the number of possible combos is called the multiplication principle.

Thus,

There are 96 different possible combos.

The principle used to calculate the number of possible combos is called the multiplication principle.

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The rejection region is t > 1.761.

To test the hypothesis that the mean fee for car washers (including tips) is greater than $12, we can perform a one-sample t-test.

Sample mean [tex]\bar{x}[/tex]  = $14.9

Sample standard deviation (s) = $6.75

Sample size (n) = 15

Significance level (α) = 0.05 (5%)

Since the sample size is small (n < 30) and the population standard deviation is unknown, we will use the t-distribution for inference.

Define the null and alternative hypotheses:

Null hypothesis (H₀): μ ≤ $12 (Mean fee for car washers is less than or equal to $12)

Alternative hypothesis (H₁): μ > $12 (Mean fee for car washers is greater than $12)

Determine the critical value (rejection region) based on the significance level and degrees of freedom.

The degrees of freedom (df) for a one-sample t-test is calculated as df = n - 1 = 15 - 1 = 14.

Using a t-table or statistical software, we find the critical t-value for a one-tailed test with α = 0.05 and df = 14 to be approximately 1.761.

Calculate the test statistic:

The test statistic for a one-sample t-test is given by:

t = ([tex]\bar{x}[/tex]  - μ) / (s / √n)

Plugging in the values:

t = ($14.9 - $12) / ($6.75 / √15) ≈ 2.034

Make a decision:

If the test statistic t is greater than the critical t-value, we reject the null hypothesis. Otherwise, we fail to reject the null hypothesis.

In this case, the calculated t-value (2.034) is greater than the critical t-value (1.761), indicating that it falls in the rejection region.

State the conclusion:

Based on the test results, at the 5% significance level, we have enough evidence to reject the null hypothesis.

We can infer that the mean fee for car washers (including tips) is greater than $12.

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