求函数的值域是研究函数的重要内容,求函数值域的方法很多,在初中教学中无固定模式,教学有法,但无定法,意在开拓学生的思维和培养学生的创造力。基本方法有:观察法、反函数法、配方法、换元法、判别式法、不等式法、数形结合法。 Seeking the value range of the function is an important part of the research function. There are many ways to find the value range of the function. There is no fixed pattern in the teaching of junior high school. There is a method of teaching, but there is no definite method. It is intended to open up students ’thinking and cultivate students’ creativity. The basic methods are: observation method, inverse function method, with the method, for yuan method, discriminant method, inequality method, the number of combination method.