Question

Two parabolas are the graphs of the equations $y=2x^2-10x-10$ and $y=x^2-4x+6$. give all points where they intersect. list the points in order of increasing $x$-coordinate, separated by semicolons.

Answer 1

(-2, 18) and (8, 38)

Explanation:

First, set the two equations equal to each other to get $2x^2-10x-10=x^2-4x+6$. Combine like terms to get $x^2-6x=16$. To complete the square, we need to add $\left(\dfrac{6}{2}\right)^2=9$ to both sides, giving $(x-3)^2=16+9=25$.

So we have $x-3=\pm5$. Solving for $x$ gives us $x=-2$ or $8$. Using these in our original parabolas, we find the points of intersection to be $\boxed{(-2,18)}$ and $\boxed{(8,38)}$.

Credit: AoPs

Answer 2

(-2,18):(8,38) Set them equal to each other you get, x^2-6x-16=0, you can factor to get, (x-8)(x+2) to get solutions 8,2 for the x values then plug in for y values.