The sign of the square term of x is positive, the opening of the quadratic function is upward, and the symmetry axis is determined according to the function. X makes the function greater than or equal to zero in the interval of (0, 1/2). Then, when x=0, the function value is 1. The symmetry axis is -a/2, and there are several intersections between the function in question and the X axis. Start the discussion:

A minus 4 is less than or equal to zero, and the function scale is greater than or equal to zero. Solution: -2 is less than or equal to and A is less than or equal to 2.

A minus 4 is greater than zero, the function has two intersections, and the symmetry axis is on the left side of the origin: the right intersection of the function and the X axis should be on the left side of the origin, and find a root X2 of the function to make it less than 0; Symmetry axis is on the right side of the origin: the left intersection of the function and the X axis should be on the right side of the origin. Solve one of the functions with X 1 to make it greater than zero. In short, x=0 and = 1/2 cannot be distributed on both sides of the symmetry axis and the intersection point.