Write the equation of the quadratic function in standard form represented by the graph

The most efficient method for this problem is completing the square, because the equation has a perfect square trinomial on its left side.

This is because x² + 6x + 9 can be factored to (x + 3)², which is a perfect square trinomial. The reason this makes completing the square the most efficient method is because if you complete the square of x² + 6x + 9 you get (x + 3)², so then the equation becomes:

(x + 3)² = 16, and this can be solved easily.

I hope this helps!