For the function to be established, the root number must be greater than or equal to 0, and the root number is a quadratic equation, so there are two situations:

1, m=0, and the constant holds.

2. When m is not equal to 0, in order to make the root sign greater than 0, according to the nature of the quadratic equation of one variable, the opening must be upward, so m is greater than 0, and there is at most one intersection point with the X axis (at this time, the intersection state is equal to 0, and the non-intersection state is greater than 0). Only when these two conditions are met can the value of m be solved.

The final conclusion is that the first and second cases can be used to get the final value range.