Use the intercept form of the equation of a parabola, y=a(x-p)(x-q).
y=- 2(x-9)(x-1)
Practice makes perfect
We want to write the equation of the parabola that passes through the point (0,- 18) and has x-intercepts 9 and 1. To do so, we will use the intercept form of a quadratic function.
y=a(x-p)(x-q)
In this form, p and q are the intercepts. Therefore, we can partially write our equation.
y=a(x-9)(x- 1)
Finally, since the parabola passes through the point (0,- 18), we can substitute 0 for x and - 18 for y in our partial equation to solve for a.
