Question

Consider the function f(x) = x2 + 2x – 15. What are the x-intercepts of the function? Left-most x-intercept: ( , 0) Right-most x-intercept: ( , 0)

Answer 1

Left-most x-intercept: (-5, 0)

Right-most x-intercept: (3, 0)

Answer 2

(- 5, 0) and (3, 0)

Explanation:

Given

f(x) = x² + 2x - 15

To find the x- intercepts let f(x) = 0, that is

x² + 2x - 15 = 0 ← in standard form

(x + 5)(x - 3) = 0 ← in factored form

Equate each factor to zero and solve for x

x + 5 = 0 ⇒ x = - 5 ← left x- intercept

x - 3 = 0 ⇒ x = 3 ← right x- intercept