Answer:
3
Step-by-step explanation:
Intersections on the x axis occur when y = 0. f(x) is another term for y, so set f(x) equal to zero and solve for the two possible x's.
0 = x^2 - 3x - 40
0 = (x-8)(x+5)
By solving for x, you get 8 and -5. 8 and -5 added together will equal 3.
