已知定义域为R的函数f(x)=2*x+1+a分之-2*x+b是奇函数求f(x)值域

∵f(x) = (-2^x+b)/(2^x+1+a)是奇函数
∴f(-x) = -f（x),即：
{-2^(-x)+b}/{2^（-x)+1+a} = -(-2^x+b)/(2^x+1+a)
-{2^(-x)-b}/{2^（-x)+1+a} = (2^x-b)/(2^x+1+a)
{2^（-x)+1+a} × (2^x-b) = -{2^(-x)-b} × (2^x+1+a)
2^0 +（a+1)2^x -b2^(-x) - b（a+1) = -2^0 + b2^x - （a+1)2^(-x) + b(a+1)
1 +（a+1)2^x -b2^(-x) - b（a+1) = -1 + b2^x - （a+1)2^(-x) + b(a+1)
(a-b+1)2^x + (a-b+1)2^(-x) + 2 (-ab-b+1) = 0
a-b+1=0,且-ab-b+1 = 0
b=±1,
b=-1时,a=-2；b=1时,a=0
当a=0,b=1时：
f(x) = (-2^x+1)/(2^x+1) = (-2^x-1+2)/(2^x+1) = -1 + 2/(2^x+1)
2^x＞0
2^x+1＞1
0＜1/(2^x+1)＜1
0＜2/(2^x+1)＜2
-1＜-1+2/(2^x+1)＜1
值域：（-1,1)
当a=-2,b=-1时：
f(x) = (-2^x-1)/(2^x-1) = {-(2^x-1)-2}/(2^x-1) = -1 -2/(2^x-1)
2/(2^x-1)≠0
-1-2/(2^x-1)≠-1
值域：（-∞,-1）,（-1,+∞）