Question

The image of a parabolic lens is traced onto a graph. The function f(x) = (x + 8)(x – 4) represents the image. At which points does the image cross the x-axis?

(–8, 0) and (4, 0)
(8, 0) and (–4, 0)
(2, 0) and (–1, 0)
(–2, 0) and (1, 0)

Answer 1

Set f(x)=0: (x+8)(x−4)=0 so x=−8 or x=4. Thus the image crosses the x-axis at (−8, 0) and (4, 0).