Answer:
D. y = (x - 3)(x - 6)
Explanation:
The graph shows a parabola and the parabola intersects the x-axis at (-6, 0) and at (-3, 0). When a function intersects the x-axis, the y value must automatically equal 0, since there is only horizontal movement on the x-axis.
(x-3)(x-6) is a binomial expression that will make a quadratic equation when expanded. We refer to the coordinate where a parabola intersects the x-axis as roots, which are numbers that make the quadratic equation equal 0.
We know from the zero-product property, that when the product of two numbers is 0, at least on the numbers must be 0 (e.g., 4 * 0 = 0 or even 0 * 0 = 0). Thus, we can solve any quadratic equation in the the x-intercept form (i.e., the form tha (x-3)(x-6) is currently in) by setting both expressions equal to 0 and solving for x. This wil give an x-coordinate both times, but since you set the equations equal to 0, you know that your y-coordinate each time is 0:
Solution for x - 3 = 0:
x - 3 = 0
x = 3
Solving for x - 6 = 0
x - 6 = 0
x = 6
You can check by plugging in 3 for x and 6 for x and see if you get 0:
3 for x:
(3 - 3)(3 - 6) = 0
0 * -3 = 0
0 = 0
6 for x:
(6 - 3)(6 - 6) = 0
3 * 0 = 0
0 = 0