Write a function in any form that would match the graph shown below.

  y = 2(x +1)(x -4)

Step-by-step explanation:

The intercepts are at grid points, so it is easiest to make use of those. For an x-intercept of "a", one of the factors of the function is (x -a). Here, the x-intercepts are -1 and +4, so the function has factors (x +1)(x -4).

When x=0, the product of these factors is (1)(-4) = -4, so there is a vertical scale factor of 2 to make the y-intercept be -8. The function can be written as ...

  y = 2(x +1)(x -4)