Don completes the square for the function y = x2 + 6x + 3. Which of the following functions reveals the vertex of the parabola?

A. y = (x + 3) 2 - 3

B. y = (x + 3) 2 - 6

C. y = (x + 2) 2 - 6

D. y = (x + 2) 2 - 3

B is the function in vertex form.

To complete the square, we take 1/2 of the b value (the coefficient of x) and square it:

(6/2) ² = 3² = 9

We will add and subtract this value to the function:

y = x² + 6x + 9 + 3 - 9

y = (x+3) ² + 3 - 9

y = (x+3) ² - 6