Exercise 2.4.2: Proving statements about rational numbers with direct proofs. About Prove each of the following statements using a direct proof. (a) The product of two rational numbers is a rational number. Solution (b) The quotient of a rational number and a non-zero rational number is a rational number. Solution (c) If x and y are rational numbers then is also a rational number.

Answers

Answer 1

Answer:

See Explanation

Step-by-step explanation:

(a) Proof: Product of two rational numbers

Using direct proofs.

Let the two rational numbers be A and B.

Such that:

[tex]A = \frac{1}{2}[/tex]

[tex]B = \frac{2}{3}[/tex]

The product:

[tex]A * B = \frac{1}{2} * \frac{2}{3}[/tex]

[tex]A * B = \frac{1}{1} * \frac{1}{3}[/tex]

[tex]A * B = 1 * \frac{1}{3}[/tex]

[tex]A * B = \frac{1}{3}[/tex]

Proved, because 1/3 is rational

(b) Proof: Quotient of a rational number and a non-zero rational number

Using direct proofs.

Let the two rational numbers be A and B.

Such that:

[tex]A = \frac{1}{2}[/tex]

[tex]B = \frac{2}{3}[/tex]

The quotient:

[tex]A / B = \frac{1}{2} / \frac{2}{3}[/tex]

Express as product

[tex]A / B = \frac{1}{2} / \frac{3}{2}[/tex]

[tex]A / B = \frac{1*3}{2*2}[/tex]

[tex]A / B = \frac{3}{4}[/tex]

Proved, because 3/4 is rational

(c) x + y is rational (missing from the question)

Using direct proofs.

Let x and y be

Such that:

[tex]x = \frac{1}{2}[/tex]

[tex]y = \frac{2}{3}[/tex]

The sum:

[tex]x + y = \frac{1}{2} + \frac{2}{3}[/tex]

Take LCM

[tex]x + y = \frac{3+4}{6}[/tex]

[tex]x + y = \frac{7}{6}[/tex]

Proved, because 7/6 is rational

The above proof works for all values of A, B, x and y; as long as they are rational values


Related Questions

what is the answer
y-11=25-3y

Answers

Answer:

9

Step-by-step explanation:

y-11=25-3y

y + 3y = 25 + 11

4y = 36

y = 36 / 4

y = 9

Hope it will help :)

Pls help I’ll brainlest

Answers

Answer:

8

Step-by-step explanation:

Jeremiah bought x toy sets for $20 each and then a video game for $60. Jeremiah spent a total of $220. How may toy sets did he buy?

To find our answer, we can solve the equation:

20x + 60 = 220

        -60    -60

20x = 160

/20    /20

x = 8

Jeremiah bought 8 toy sets!

I hope this helps :)

Dara:240g
Brüt kütle:760g
Net Kütle:.....g
işlem:​

Answers

Answer:

Net Mass = 520 g

Step-by-step explanation:

Given:

Waste = 240 g

Gross mass = 760 g

Find:

Net Mass

Computation:

Net Mass = Gross mass - Waste

Net Mass = 760 g - 240 g

Net Mass = 520 g

Pls help 20 points this question is for my friend

Answers

Answer:

750 cubic feet

Step-by-step explanation:

A stack of 500 pieces of paper is 1.9 inches tall. How thick is each piece of paper?

Answers

Answer:

0.00375 inches thick

Solve the right triangle round your answer to the nearest tenth

Answers

Answer/Step-by-step explanation:

✔️A = 180° - (50° + 90°) (sum of triangle)

A = 40°

✔️Find a:

Reference angle = 50°

Opposite = 17

Adjacent = a

Therefore, using trigonometric ratio, we have the following:

Tan 50 = 17/a

a = 17/tan 50

a = 14.3 (nearest tenth)

✔️Find c using Pythagorean Theorem:

c² = a² + b²

c² = 14.3² + 17²

c = √493.49

c = 22.2 (nearest tenth)

Malcolm buys a 5/6-pound bag of black beans and a 3/4-pound bag of pinto

Answers

Answer:

1 7/12

Step-by-step explanation:

I think that you want to know how many total pounds of beans do you have.

Well, to find this, simply find the LCM of 6 and 4. That is 12.

So convert the fractions to have a denominator of 12.

10/12, 9/12

Now add:

(10+9)/12 = 19/12 = 1 7/12

In a bag, there are ten identical balls, numbered 1 to 10. You let two persons, each pick one ball from the bag. Suppose the person who gets ball of 10 can get some reward, so each one prefers to get ball of 10. As we easily know, the probability of getting ball 10 for first person is 1/10. What is the probability of getting ball 10 for second person

Answers

1/10 because amongst 10 balls there is only one 10th ball there by making only one possible chance of getting ball no 10

Algebra roller coaster building it most state from the ground and it have to be 100ft

Answers

Answer:

sa taas nito ay 50 square meter kung pagbabasihan mo sa ibaba 55 square meter malaki rin sa baba kaya ang tawag dyaan ay centementer

I hope I can help you and give me a star even if I am only 5 or 4 stars and please put a heart for many

Solve the formula A=2πrh+2πr2 for h.

Answers

Answer:

h = (A - 2πr²)/(2πr)

General Formulas and Concepts:

Pre-Algebra

Order of Operations: BPEMDAS

Brackets Parenthesis Exponents Multiplication Division Addition Subtraction Left to Right  

Equality Properties

Multiplication Property of Equality Division Property of Equality Addition Property of Equality Subtraction Property of Equality

Algebra I

Terms/Coefficients

Step-by-step explanation:

Step 1: Define

A = 2πrh + 2πr²

Step 2: Solve for h

[Subtraction Property of Equality] Subtract 2πr² on both sides:                 A - 2πr² = 2πrh[Division Property of Equality] Divide 2πr on both sides:                            (A - 2πr²)/(2πr) = hRewrite/Rearrange:                                                                                        h = (A - 2πr²)/(2πr)

Can you guys help me and answer this math question below please I’ll mark brainliest to whoever answers

Answers

the answer to this problem is (2,4)

Answer:

Your answer will be (2,4) :)

A restaurant chef made 4 1/2 pints of mushroom soup Each bowl of soup holds 1/2 of pint. How many bowls of soup will.the chef be able to fill?

Answers

Answer:

4 2/4

Step-by-step explanation:

4 1/2 + 1/2 = 4 2/4

i just added em up

Answer:

Step-by-step explanation: 4 1/2 pints / 1/2 pint/ bowl = (9/2) / (1/2) = 9/2 pints x 2 bowl/pint = 18/2 bowls = 9 bowls. QED.

Help person right gets brainlist​

Answers

correct answer is = 3 17/28
brainliest?
P= 3 17/28
If its mixed number

P=3.60714285
If its need to be decimal

Just copy the answer from the pic



Jollibee employs a total of 10 cashiers and 15 kitchen crews. The manager selects a team of 2 cashiers and

4 kitchen crews for a graveyard shift. In how many ways can the manager select a team?

Answers

Answer:

The manager can select a team in 61425 ways.

Step-by-step explanation:

The order in which the cashiers and the kitchen crews are selected is not important. So we use the combinations formula to solve this question.

Combinations formula:

[tex]C_{n,x}[/tex] is the number of different combinations of x objects from a set of n elements, given by the following formula.

[tex]C_{n,x} = \frac{n!}{x!(n-x)!}[/tex]

In how many ways can the manager select a team?

2 cashiers from a set of 10.

4 kitchen crews from a set of 15. So

[tex]T = C_{10,2}*C_{15,4} = \frac{10!}{2!(10-2)!}*\frac{15!}{4!(15-4)!} = 45*1365 = 61425[/tex]

The manager can select a team in 61425 ways.

CEOLATIONS AND INEQUALITIES
Finding angle measures of a triangle given angles with variables
In the triangle below, suppose that m U=(x+9)°, m = (2x+1), and mW=(7x)".
Find the degree measure of each angle in the triangle.

Answers

Answer:

seventeen degrees(17⁰)


What decimal does the model represent?
The model below is shaded to represent 2
A 25.6
2.056
2.56
0.256

Answers

Answer:

2.56

Step-by-step explanation:

The answer is 2.56 tyytttttggggg

digits to write the value of the 5 in this number.587,096​

Answers

Answer: what does the question even mean

Step-by-step explanation:

5.87096 x 10^-1 Is that what you are looking for?

y=−2x+1
x−3y=11 find the solution using elimination.

Answers

Answer:

Step-by-step explanation:

Using first equation in the second gives you

x-3(-2x+1)=11

x+6x-3=11

7x-3=11

7x=14

x=2, making y=-2x+1 become

y=-2(2)+1

y=-4+1

y=-3 so the solution is the point

(2,-3)

Triangle ABC is shown below.
What is the cosine of angle B?

Answers

I think it’s b ?bbbbb

The cosine of angle ∠B will be 3 / 5. Then the correct option is C.

What is trigonometry?

The connection between the lengths and angles of a triangular shape is the subject of trigonometry.

The cosine of the angle θ is the ratio of the side adjacent to the angle and the longest length of the triangle which is the hypotenuse.

cos θ = base / hypotenuse

Triangle ABC is shown below. The side BC is base which is equal to 3. And the side AB is hypotenuse which is equal to 5.

Then the cosine of the angle ∠B will be given as,

cos θ = base / hypotenuse

cos B = 3 / 5

The cosine of angle ∠B will be 3 / 5. Then the correct option is C.

More about the trigonometry link is given below.

https://brainly.com/question/22698523

#SPJ2

which one is the answer

Answers

Answer:

Two

Step-by-step explanation:

The radii of the pedal sprocket, the wheel sprocket, and the wheel of the bicycle in the figure are 4 inches, 2 inches, and 14 inches, respectively. A cyclist is pedaling at a rate of 1 revolution per second.

(a) Find the speed of the bicycle in feet per second and miles per hour.
ft/sec
mph

(b) Use your result from part (a) to write a function for the distance d (in miles) a cyclist travels in terms of the number n of revolutions of the pedal sprocket.
d =


(c) Write a function for the distance d (in miles) a cyclist travels in terms of time t (in seconds). Compare this function with the function from part (b).
d =

Answers

C is the answer!!! :D

Find the pattern and use it to list the next two terms in the sequence.
-3,6,-28,72,-360,2160, ___ ,___

Answers

Answer:

Step-by-step explanation:

a₁ = -3 = (-1)¹×3

a₂ = 6 = (-1)²×2×3

a₃ = -28 = (-1)³×2²×7

a₄ = 72 = (-1)⁴×2³×3²

a₅ = -360 = (-1)⁵×2³×3²×5

a₆ = 2160 = (-1)⁶×2⁴×3³×5

That's as far as I got. I can predict that a₇ is a multiple of -32 and a₈ is a multiple of 64, but I don't see the pattern with the other factors.

Solve the equation 6X+2=74

Answers

Divide 2 by 74 and simplify into brackets
Subtract 2 to both sides of the equation, leaving you with 6X= 72. Then, divide both sides by 6 which would leave you with x= 12.
Hope it helps.

Jolyn was paid $340 last week working 17 hours. What was Jolyn’s hourly pay? Do not include the units in your answer

Answers

Answer:

20

Step-by-step explanation:

It is mentioned that Jolyn made $340 in 17 hours last week. In order to evaluate this, you'll have to divide the money earned by the hours worked.

[tex]\frac{340}{17} =20[/tex]

Therefore, Jolyn makes $20 an hour as 20 x 17 = 340 which is correct,

Which of the following are accurate factors of 4x2 + 5.0 – 21 when multiplied together? Select the two correct answers.
(2 points)
(40 - 7)
0 (x + 2)
(52 -3)
0 (+3)

Answers

Answer:

First and last

Step-by-step explanation:

(4x - 7) (x + 3)

FOIL

4x^2 + 5x - 21

Kevin is driving on a long road trip. He currently has 11 gallons of gas in his car. Each hour that he drives, his car uses up 1.75 gallons of gas. How much gas would be in the tank after driving for 5 hours? How much gas would be left after t hours?

Answers

Answer:

He would have 2.75 gallons left after 5 hours.

Step-by-step explanation:

the triangle Loom is made from wood strips shaped into a 45 45 90 triangle. pegs are placed every half inch along the hypotenuse and every quarter inch along each leg. suppose you make a loom with an 18 inch hypotenuse. approximately how many pegs will you need ​

Answers

Answer:

36 pegs (for the hypotenuse)

About 51 pegs (for the legs)

138 pegs (total)

Step-by-step explanation:

Along the hypotenuse, the pegs are placed every half-inch. That would make 2 pegs per inch. Multiply 2 x 18 to get 36.

The legs are each 9 sqrt 2. This is 12.7279220614. The pegs are placed at each quarter inch for the legs. This is 4 per inch. So multiply 12.7279220614 x 4 to get 50.9116882454. Round this to 51.

Add 51 + 51 for the legs total pegs. You get 102. Add 102 + 36 to get 138 pegs total.

Hope it helps!

PLEASEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE HELP ME WILL GIVE BRAILIST

Answers

Answer:

a) 24[tex]ft^2[/tex]

b) 52ft

Step-by-step explanation:

a)

This question asks to find the capacity of the container. This is essentially asking what the volume of the container is. This can be done by multiplying the length by the width by the height.

4 * 2 * 3

= 24

b)

This question is asking how much material was used to make the prism. This is essentially asking what the surface area of the prism is. This can be found by finding the area of all the sides of the prism and then adding it up. Since it is a rectangular prism, opposite faces are congruent, hence one only has to find the area of three faces, add it up, then multiply it by two to find the answer.

2 ( 4 * 2 ) + 2 ( 3 * 4 ) + 2 ( 2 * 3 )

= 2(8) + 2(12) + 2(6)

= 16 + 24 + 12

= 52

Write an integer for deposit of $100

Answers

Write an integer for deposit of $100:

-$100

Solve the inequality for x.
X-3/4>=-1/8
Simplify your answer as much as possible

Answers

ExplanationGiven the Inequality.

[tex]x - \frac{3}{4} \geqslant - \frac{1}{8} [/tex]

Solve the Inequality for x-term.

[tex]x \geqslant - \frac{1}{8} + \frac{3}{4} [/tex]

Make both fractions to have same denominators by multiply 2 in 3/4 for both numerator and denominator.

[tex]x \geqslant - \frac{1}{8} + \frac{3 \times 2}{4 \times 2} \\ x \geqslant - \frac{ 1}{8} + \frac{6}{8} \\ x \geqslant \frac{5}{8} [/tex]

Hence, the solution is, "x is greater or equal to 5/8."

Answer

[tex] \large \boxed{x \geqslant \frac{5}{8} }[/tex]

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