What is f(x) = 2x2 + 28x – 5 written in vertex form?

Factor 2 from the quadratic and linear terms: f(x) = 2(x² + 14x) − 5. Complete the square inside the parentheses by adding 49, since half of 14 is 7 and 7² = 49: f(x) = 2[(x + 7)² − 49] − 5 = 2(x + 7)² − 103. Therefore, the vertex form is 2(x + 7)² − 103, choice B.

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