What is f of x is equal to 8 x squared plus 4 x written in vertex form?

Complete the square by factoring 8 from the quadratic and linear terms: f(x) = 8(x² + ½x). Half of ½ is ¼, and its square is 1/16, so f(x) = 8[(x + ¼)² − 1/16] = 8(x + ¼)² − ½. Thus the vertex form is choice D.

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