1. Matching method formulizes the function into vertex format, and then obtains the range of the function according to the defined range of the function. ?

Second, the separation of constants This is generally for fractional functions. Try to match the function on the numerator to the same form as the denominator, and separate the constants to get the range.

Third, the reverse order method for the form of y= a certain X, you can use the reverse order method to express x= a certain Y. At this time, you can see the limit range of Y, which is the value range of the original formula.

Four, method of substitution for a part of the function, more complex or unfamiliar, you can use method of substitution, the function into a familiar form, from which to solve.

Fifth, monotonicity can first find the monotonicity of the function (pay attention to the definition domain first), and then find the range of the function in the definition domain according to the monotonicity. ?

The basic inequality of intransitive verbs According to the basic inequality we have learned, we can transform the function into the applicable basic inequality to find the domain. ?

Seven, the combination of numbers and shapes can draw the graph of the function according to the formula given by the function, find the corresponding point on the graph, and find the value range.

Eight, the derivative method to find the derivative of the function, observe the definition domain of the function, compare the endpoint value and the extreme value, and find the maximum and minimum value, and you can get the value domain.

In the classical definition of a function, the range of values changed due to the change of variables is called the range of values of the function, while in the modern definition of a function, it refers to the set of all images corresponding to all elements in the definition domain under a corresponding law. F: In a → b, the range is a subset of set B. If f(x)=x, then the range of f(x) is the range of function f(x).