Answer:
x = ±√13 - 8
Explanation:
Move the constant term to the right side of the equation.
x² + 16x + 51 = 0
x² + 16x = -51
We complete the square by taking half of the coefficient, squaring it, and adding it to both sides of the equation. The formula is (b/2)².
x² + 16x = -51
here the formula would be (16/2)² = 64
x² + 16x + 64 = -51 + 64
Now just simplify by factoring the left side and adding up the right side.
(x + 8)² = 13
You have to isolate x to find what it equals. Here start by taking the square root of both sides
x + 8 = √13
Subtract 8 to both sides
x = ±√13 - 8