Answer:
x = - 2, x = 7
Step-by-step explanation:
Given
f(x) = 4x² - 20x - 56
To find the zeros let f(x) = 0, that is
4x² - 20x - 56 = 0 ( divide through by 4 )
x² - 5x - 14 = 0 ← in standard form
(x - 7)(x + 2) = 0 ← in factored form
Equate each factor to zero and solve for x
x + 2 = 0 ⇒ x = - 2
x - 7 = 0 ⇒ x = 7
