Rewrite the quadratic function in standard form by completing the square.
-$$f ( x ) = x ^ { 2 } - 8 x$$
A) $f ( x ) = ( x + 8 ) ^ { 2 } - 8$
B) $f ( x ) = ( x + 4 ) ^ { 2 } - 4$
C) $f ( x ) = ( x - 4 ) ^ { 2 } - 16$
D) $f ( x ) = ( x - 8 ) ^ { 2 } - 64$

Question

Quizplus · Accepted Answer

To complete the square for the quadratic function $f(x) = x^2 - 8x$, we add and subtract $(\frac{8}{2})^2 = 16$ inside the function: $f(x) = x^2 - 8x + 16 - 16$. This simplifies to $f(x) = (x - 4)^2 - 16$, which matches option C.

Rewrite the Quadratic Function in Standard Form by Completing the Square