Question

Find the zeros of y=x^2+4x-9 by completing the square.

Answer 1

`\boxed{x =-2 \±√(13) }`

Explanation:

Let y = 0

0 = x^2+4x-9

x² + 4x -9 = 0

Add 9 on both sides.

x² + 4x = 9

(b/2)² = (4/2)² = 2² = 4

Add 4 on both sides.

x² + 4x + 4 = 13

Facror left side.

(x+2)² = 13

Take the square root on both sides.

x + 2 = ±√13

Subtract 2 on both sides.

x = ±√13 - 2