determine the equation of a quadratic function

题目

determine the equation of a quadratic function
conditions:x-intercept 3,and passing through the point (1,-2)

答案

It sounds like that it passes thru 3 points:　(0,0),(3,0),(1,-2)From the first 2 points,it can be expressed in the form of y = ax(x-3)It passes thru (1 -2):-2 = a*1*(1-3)a = 1y = x(x-3)