You have 3 points and need to find ax2 + bx + c = y. First use (0,2). x is zero, so y = 2 = c. You have c. Now put (-1,0) into the equation. 0 = 1a -b + 2. Rearrange so you get b = a + 2. Now use the other point. a*(-2 squared) + b*(-2) + 2 = 0. Simplify and substitute (a + 2) for b and you will have the answer.
