Rewrite the equation by completing the square. f (x) = x^2 + 20x - 86

f (x) = (x+10) ^2 - 86

Step-by-step explanation:

f (x) = x^2 + 20x - 86 f (x) = x^2 + 20x + 100 - 86 (because (20/2) ^2 = 100) f (x) = (x+10) ^2 - 86

Completing the square means you do (b/2) ^2 where b is: a^2x + bx + c.