You can put this solution on YOUR website! It's not an answer, it's a graph.
------
Graph f(x) = 2x^2 - 4x
Use x and y
y = 2x^2 - 4x
===============
Pick values for x and find y.
Plot the points.
Draw a curve thru them.
Do as many as you like.
You can use Excel if you have it.