f(x)=log2(1-x/1+x)的值域
问题描述：
f(x)=log2(1-x/1+x)的值域
答
应该是（1-x）/（1+x）吧 不然也太简单了
f（x）=log2[(1-x)/（1+x)]
=log2[2/(x+1)-1]
2/(x+1)值域是 (-无穷,0)U(0,+无穷)
2/(x+1)-1值域是 (-无穷,-1)U(-1,+无穷)
log2[2/(x+1)-1]值域是 (-无穷,+无穷)
所以值域是 (-无穷,+无穷)