Use the method of completing the square to solve the quadratic equation. x 2 + 20 x $-$ 25 = 0
A) $x = 5 \sqrt { 5 } \pm 20$
B) $x = 20 \pm 5 \sqrt { 5 }$
C) $x = - 10 \pm 5 \sqrt { 5 }$

Question

Quizplus · Accepted Answer

To complete the square, we need to add and subtract the square of half the coefficient of x:

x^2 + 20x - 25 = 0 
x^2 + 20x + (20/2)^2 - (20/2)^2 - 25 = 0 
(x + 10)^2 - 125 = 0 
(x + 10)^2 = 125 
x + 10 = ±√125 
x = -10 ± 5√5

Therefore, the answer is C, x = -10 ± 5√5.

Use the Method of Completing the Square to Solve the Quadratic