Question

Nina knows that the average of the x-intercepts represents the line of symmetry for a quadratic function through the x-axis. Which equation represents the average of the x-intercepts for f(x) = 4x2 – 24x + 20?

StartFraction negative 5 minus 1 Over 2 EndFraction = negative 3 = –3
StartFraction negative 10 minus 2 Over 2 EndFraction = negative 4 = –4
StartFraction 1 + 5 Over 2 EndFraction = 3 = 3
StartFraction 2 + 10 Over 2 EndFraction = 4 = 4

Answer 1

Factor first: f(x) = 4(x^2 − 6x + 5) = 4(x − 1)(x − 5), so the x-intercepts are x = 1 and x = 5. Their average is (1 + 5)/2 = 3.

So the correct choice is: (1 + 5)/2 = 3.