Question 198267
{{{x^2 + 8x = 16}}}
Complete the square
{{{x^2 + 8x + (8/2)^2 = 16 + (8/2)^2}}}
{{{x^2 + 8x + 16 = 16 + 16}}}
The left side is a perfect square
{{{(x + 4)^2 = 32}}}
Take the square root of both sides
{{{x + 4 = sqrt(32)}}}
{{{x + 4 = 4*sqrt(2)}}}
{{{x = 4*(-1 + sqrt(2))}}}
and
{{{x = 4(-1 - sqrt(2))}}}
Note there are 2 answers since there is a
(+) and a (-) square root
I checked the 2nd answer -OK
Try checking the 1st