代换法是一重要的数学方法,在中学数学乃至高等数学的学习中都有着广泛的应用。运用它常常可使问题化繁为简,化难为易。本文仅就利用代换法求函数值域加以说明。例1 求函数的值域, 解∵,故设(x-1)~(1/2)=t(t≥0)则 x=t~2+1 从而 y=-t~2+t-1(t≥0) ∵例2 求函数的值域。 Substitution method is an important mathematical method. It has a wide range of applications in middle school mathematics and even advanced mathematics. The use of it can often make the issue simple and easy to use. This article only uses the substitution method to find the function range. Example 1 Find the value range of the function and solve the problem, so set (x-1)~(1/2)=t(t≥0) then x=t~2+1 and y=-t~2+t-1 (t≥0) Example 2 Find the range of the function.