When x is equal to, the quadratic function y is negative, and the square of X has the maximum value

When x is equal to, the quadratic function y is negative, and the square of X has the maximum value

x=-b/2a

Given the quadratic function y = - x square + 10x-17, if the value of Y is less than or equal to 8, and greater than or equal to 4, then the value range of X

y=-x²+10x-17
=-(x²-10x+25-25)-17
=-(x-5)²+8
four

Given that y = - (xsquare) + 2aX + 1-A has a maximum value of 2 when x is greater than or equal to 0 and less than or equal to 1, find the value of A

The verification discriminant is always greater than 0
Classified discussion
When the axis of symmetry a < 0, f (0) = 2, a = - 1
When a > 1, f (1) = 2, a = 2
When 0 < a < 1, f (a) = 2, there is no solution