n a study to investigate whether vitamin C will prevent colds, 400 subjects are assigned at random to one of two groups. The experimental group takes a vitamin C tablet daily, while the control group takes a placebo. At the end of the experiment, the researchers calculate the difference between the percentage of subjects in the two groups who were free of colds. This difference is statistically significant (P=0.03) in favor of the vitamin C group.

Answer:

The price per gallon of gas with a $7 car wash is $3.19

Then if you purchase x gallons of gas and also pay for the car wash, the total cost is:

C(x) = $7 + $3.19*x

In the case that you do not pay for the car wash, the cost per gallon is $3.39

Then the cost for x gallons of gas in this case is:

K(x) = $3.39*x

When is it worth it to buy the car wash?

We need to sett the equations:

C(x) = K(x)

This means that you pay exactly the same in both cases, but in one ( C(x)) you get the car wash and in the other not.

Then we need to solve:

$7 + $3.19*x = $3.39*x

$7 = ($3.39 - $3.19)*x = $0.20*x

$7/$0.20 = x = 35

Then for 35 gallons, is worth to buy the car wash.

In the case where the car wash costs $2, then the equation C(x) becomes:

C(x) = $2 + $3.19*x

Then if we solve the same equation:

C(x)  =K(x)

$2 + $3.19*x = $3.39*x

$2 = ($3.39 - $3.19)*x

$2 = $0.20*x

$2/$0.20 = x

10 = x

Then for 10 galons is whort  buy the car wash.

Answer:

[tex]\displaystyle \lim_{x\to \infty}\frac{3x^2+4.5}{x^2-1.5}=3[/tex]

Step-by-step explanation:

We want to evaluate the limit:

[tex]\displaystyle \lim_{x\to \infty}\frac{3x^2+4.5}{x^2-1.5}[/tex]

To do so, we can divide everything by x². So:

[tex]=\displaystyle \lim_{x\to \infty}\frac{3+4.5/x^2}{1-1.5/x^2}[/tex]

Now, we can apply direct substitution:

[tex]\Rightarrow \displaystyle \frac{3+4.5/(\infty)^2}{1-1.5/(\infty)^2}[/tex]

Any constant value over infinity tends towards 0. Therefore:

[tex]\displaystyle =\frac{3+0}{1+0}=\frac{3}{1}=3[/tex]

Hence:

[tex]\displaystyle \lim_{x\to \infty}\frac{3x^2+4.5}{x^2-1.5}=3[/tex]

Alternatively, we can simply consider the biggest term of the numerator and the denominator. The term with the strongest influence in the numerator is 3x², and in the denominator it is x². So:

[tex]\displaystyle \Rightarrow \lim_{x\to\infty}\frac{3x^2}{x^2}[/tex]

Simplify:

[tex]\displaystyle =\lim_{x\to\infty}3=3[/tex]

The limit of a constant is simply the constant.

We acquire the same answer.

Answer:

7x + 3

Step-by-step explanation:

Let's simplify step-by-step.

8x + 7 − x − 4

= 8x + 7 + −x + −4

Combine Like Terms:

= 8x + 7 + −x + −4

= (8x + −x) + (7 + −4)

= 7x + 3

Answer:

= 7x + 3

hope this helps and is right. p.s i really need brainliest :)

if my answer is wrong then I am incredibly sorry!

Answer:

9

Step-by-step explanation:

Answer:

f(4) = 7

Step-by-step explanation:

The notation for these type of problems is very confusing. Just remember that f(x) is the same thing as y (or some variable). Even if there is a number or something on the inside of the parentheses, it's still just a variable.

In our case

f(a) = 2(a + 4) -9

could be rewritten as

y = 2(a + 4) - 9

the thing on the inside of the parentheses signifies what the equation is dependent on.

so when is says f(4), it just want's you to trade out a for a 4, but the equation is still the same.

f(4) = 2((4) + 4) - 9

Now, just follow the order of operations

f(4) = 2(8) - 9

f(4) = 16 - 9

f(4) = 7