Quadratic function. 1. The quadratic function y = AX2 + BX + C passes through (1, - 1) (2,1) (- 1,1) to find the analytic expression of the quadratic function 2. The vertex of the parabola y = X2 - (a + 2) x + 9 is on the x-axis 3. Given that the image of quadratic function intersects with X axis at two points a (- 2,0) B (3, O), and the maximum value of the function is 2, find the analytic expression of quadratic function

Quadratic function. 1. The quadratic function y = AX2 + BX + C passes through (1, - 1) (2,1) (- 1,1) to find the analytic expression of the quadratic function 2. The vertex of the parabola y = X2 - (a + 2) x + 9 is on the x-axis 3. Given that the image of quadratic function intersects with X axis at two points a (- 2,0) B (3, O), and the maximum value of the function is 2, find the analytic expression of quadratic function

1. Substitute the point into the formula. Solve a system of linear equations of three variables. 2. Just grasp the condition, the vertex is on the X axis, which means that the ordinate of the vertex is 0. Use the root formula to write out the expression of the ordinate so that it is equal to 0. 3. The maximum value of quadratic function is usually obtained at the vertex