y=(1-2x²)/(1+2x²)
(1+2x²)y=1-2x²
y+2yx²=1-2x²
(y+1)×2x²=1-y
2x²=(1-y)/(1+y)
因為2x²≥0
所以(1-y)/(1+y)≥0
(1+y)(1-y)≥0且1+y≠-1
(1+y)(y-1)≤0且1+y≠-1
解得-1≤y＜1
　　祝學(xué)習(xí)快樂(1+y)(1-y)≥0且1+y≠-1 (1+y)(y-1)≤0且1+y≠-1是咋來的(1+y)(1-y)≥0且1+y≠-11-y變?yōu)閥-1，多了一個負號，不等式方向要改變(1+y)(y-1)≤0且1+y≠-1(1-y)/(1+y)≥0到(1+y)(1-y)≥0且1+y≠-1咋來的不好意思，上面應(yīng)該是(1+y)(1-y)≥0且1+y≠0(1-y)/(1+y)≥0兩邊同時乘以(1+y)²得到的，1+y≠0是分母不為0