Question

Which ordered pair in the form (a, b) is a solution of this equation? 3a – 4b = 21

A.

(–2, –3)








B.

(0, 7)








C.

(–3, –2)








D.

(7, 0)

Answer 1

Plug in all the 4 answer choices with the first number in place of a and second number in place of b. Whichever makes the equation correct, is the right answer. Let's try all four.

A. (
`(-2,-3)`:

`3(-2)-4(-3)=6`. This doesn't make the equation equal 21. So this isn't the correct answer.

B. (
`(0,7)`:

`3(0)-4(7)=-28`. This doesn't make the equation equal 21. So this isn't the correct answer as well.

C. (
`(-3,-2)`:

`3(-3)-4(-2)=-1`. This doesn't make the equation equal 21. So this isn't the correct answer also.

D. (
`(7,0)`:

`3(7)-4(0)=21`. This is equal to 21, so it makes the equation correct.

ANSWER: D