Question

Given x2 + 8x - 20 = 0. Which expression below would be a correct step if solving by completing the square?

A. (x + 16)2 = 36

B. (x + 4)2 = 20

C. (x + 4)2 = 36

D. (x + 16)2 = 20

Answer 1

Work your way backwards

So say we want to test if choice D is the answer

(x + 16)^2 = 20

x^2 + 32x + 256 = 20

x^2 + 32x + 256 - 20 = 0

x^2 + 32x + 236 = 0

This is NOT the same as x^2 + 8x - 20 = 0, so choice D can't be the answer.

Answer 2

its B right? @jim_thompson5910

Answer 3

no

Answer 4

(x + 4)^2 = 20

x^2 + 8x + 16 = 20

x^2 + 8x + 16 - 20 = 0

x^2 + 8x - 4 = 0

which is NOT the same as x^2 + 8x - 20 = 0

Answer 5

ok got it..C thanks!!

Answer 6

you got it