Solve the equation $x ^ { 2 } - 8 x - 65 = 0$ by completing the square.

Name: Solve the equation $x ^ { 2 } - 8 x - 65 = 0$ by completing the square.
Brand: Quizplus
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Question

Quizplus · Accepted Answer

To solve by completing the square, we need to add and subtract $(8/2)^2=16$ inside the left-hand side of the equation:
\begin{align*}
x^2-8x-65&=0\
x^2-8x+16&=81\
(x-4)^2&=81\
x-4&=\pm 9\
x&=-5,13\
\end{align*}
Therefore, the solution is $x=-5$ or $x=13$, which is choice B.

Solve the Equation x2−8x−65=0x ^ { 2 } - 8 x - 65 = 0x2−8x−65=0

Solve the Equation $x ^ { 2 } - 8 x - 65 = 0$