we have a quadratic function
f(x) = x^2 + 2x - 15
let f(x) = y
then, y = x^2 + 2x - 15
let y = 0
x^2 + 2x - 15 = 0
Using factorization method
the factors of -15 are as follows
-1 and 15, -3 and 5, 3 and -5, 1 and -15
the only factor when we multiply that we give us -15 and when we add that will give us 2 are -3 and 5
x^2 + 5x - 3x - 15
x^2 + 5x - 3x - 15 = 0
grouping the expression
we have
x(x + 5) - 3(x + 5) = 0
(x+5) =0 or (x-3)=0
x+5 = 0 or x-3 = 0
x = 0 - 5 or x = 0 + 3
x = -5 or x = 3
x can either be -5 and 3
therefore, the maximum value is 3 and the minimum value is -5