I have been studying elementary calculus for more than 20 years in senior three. I don't know if the college entrance examination will test this knowledge.

The line in the interval is parallel to the x axis, that is, the function has an inflection point in the interval.

Substitute f(x) into g(x) and take derivative to get a quadratic function, let it be 0.

Use the formula to find two roots, so that they are in the interval.