x² + 20x = 52. Why? Completing the square is easier for this equation in comparison to completing the square for the first two equations.
x^2-8=1 becomes x^2=9, so that x=plus or minus 3. Why bother with completing the square here?
x^2 + 20x = 52
x^2 + 20x + 100 - 100 = 52
(x+10)^2 = 152
taking the sqrt of both sides:
x+10 = plus or minus sqrt(152) (and so on).
