Question

What would f(2)= be and how would you find f(x)=-65 when x =? I got the other ones but I do not understand this.

Answer 1

f(x) = x² - 2x - 80

f(2) = 2² - 2(2) - 80

f(2) = 4 - 4 - 80 = -80

x² - 2x - 80 = - 65

x² - 2x - 80 + 65 = 0

x² - 2x - 15 = 0

(x - 5)(x + 3)= 0

x = 5; x = -3