1. Substitute the three points into the equation to give three equations in three unknowns. Solve them simultaneously for a,b,c.
2. Surely you can tell me what the coordinate of the turning point is. You can also see (0,0) and (1.5, 0) lie on the curve. So either do the same thing as in part 1, or substitute the turning point into the turning point form of the quadratic and then use one of the other points to help find a.