Which function in vertex form is equivalent to f of x is equal to x squared plus 6 x plus 3 ?

Complete the square by taking half of 6, which is 3, and squaring it to get 9. Then rewrite x² + 6x + 3 as (x + 3)² − 9 + 3 = (x + 3)² − 6. So the equivalent vertex form is choice D, f(x) = (x + 3)² − 6.

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