There are many methods to find the function range, such as direct method, collocation method, monotonicity method, method of substitution method, separation constant method, basic inequality method and so on. To find the range of function values, we should first be familiar with the range of various common basic elementary functions, and then be good at choosing corresponding methods according to the structural characteristics of the resolution function. Like the definition domain, the range of a function should be written as an interval or a set.