Question

Find the missing value to complete the square.

x^2 + 8x + __ = 0

Answer 1

−x^2 − 8x

Explanation:

Lets say y is the missing value

Add -x^2 to both sides.

x^2+8x+y+−x^2=0+−x^2

8x+y=−x^2

Add -8x to both sides.

8x + y + −8x = −x^2 + −8x

y = −x^2 − 8x

So the whole equation would be

x^2 + 8x + −x^2 − 8x = 0