Answer:
y = (x + 3)² - 6
Explanation:
The equation of a parabola in vertex form is
y = a(x - h)² + k
where (h, k) are the coordinates of the vertex and a is a multiplier
Given
f(x) = x² + 6x + 3
Using the method of completing the square
add/subtract ( half the coefficient of the x- term)² to x² + 6x
f(x) = x² + 2(3)x + 9 - 9 + 3
= (x + 3)² - 6 ← in vertex form