Want to ask a high school mathematics about "the maximum value problem of quadratic function on closed interval" The problem is: find the maximum value of function y = x square - 2aX - 1 on [0,2] guys. I'm not good at math. I can't draw inferences from one instance~

Want to ask a high school mathematics about "the maximum value problem of quadratic function on closed interval" The problem is: find the maximum value of function y = x square - 2aX - 1 on [0,2] guys. I'm not good at math. I can't draw inferences from one instance~

y=(x-a)^2-1-a^2
The opening is upward, and the axis of symmetry is x = a
Classification discussion:
1) If the axis of symmetry is on the left side of the interval [0,2], i.e. A2, then ymax = y (0) = - 1, yman = y (2) = 3-4A
3) The axis of symmetry is in the interval [0,1], that is, 0=