1) did you try desmos?
2)you have to factor it. 2x^2-8x, you can remove 2x from it so it becomes x^2-4 which is a differnce of sqaures and factors out to (x-4)(x+4) so x= =/- 4. then from there to find the vertex you can eye ball it in this one because the x intercepts are nice adn centered. the x value of the vertex is going to be 0 because is right in between the x intercepts. then to find the y value, just put 0 into the eqation.
