Use the intercept form of the equation of a parabola, y=a(x-p)(x-q).
y=(x+1)(x-2)
Practice makes perfect
We want to write the equation of the parabola that passes through the point (1,- 2) and has x-intercepts - 1 and 2. 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-(- 1))(x- 2)
⇕
y=a(x+1)(x-2)
Finally, since the parabola passes through the point (1,- 2), we can substitute 1 for x and - 2 for y in our partial equation to solve for a.
