ACT math help

Question

(x + 3)(x -  4) = 8

 

Which of the following is the solution set for the equation above? Why??

 

A) {-3, 4}

B) {-4, 3}

C) {-5, 4}

D) {-4, 5}

 

 

Answer 1

A) is out, first factor would be zero

B) is out, product is -6.

C) is out, second factor would be zero.

D) well guess what!

Answer 2

Put it in the form of a quadratic equation and solve it.

 

(x + 3)(x - 4) = 8

 

x² - 4x + 3x - 12 = 8

 

x² - x - 20 = 0

 

(x - 5)(x + 4) = 0

 

x = -4 or 5

 

Answer D is correct.