Question

Complete the square to re-write the quadratic function in vertex form:
y = x2 + 4x – 9

Answer 1

y = (x + 2)² - 13

Explanation:

y = x² + 4x - 9

To complete the square

add/ subtract ( half the coefficient of the x- term)² to x² + 4x

y = x² + 2(2)x + 4 - 4 - 9

= (x + 2)² - 13 ← in vertex form

Answer 2

Answer: − 2 ± √ 13

Explanation:

(-b±√(b²-4ac))/(2a)

Plug in and solve.