Answer :
Hi there!
[tex]\large\boxed{x = -12, 3}[/tex]
The roots of a function are when f(x) = 0, so:
0 = x² + 9x - 36
Find two numbers that multiply to -36 and add up to 9.
We get the numbers 12 and -3, so:
0 = (x + 12)(x - 3)
Set each equal to 0 to find the x value:
0 = x + 12
x = -12
0 = x - 3
x = 3