That's what it usually says at the beginning. Then it is the difference f(x 1)-f(x2).

Next, we should use factorization flexibly in the calculation (work it out by ourselves)

Get the product form of two or more algebraic expressions

Finally, according to the domain and X 1 < X2, the symbol of algebraic product is judged, and the symbol of the whole algebraic expression is obtained.

How did I basically do it? I don't know if you are useful.