y=(1-2x²)\(1+2x²) 如何用反解法求

y=(1-2x²)/(1+2x²)
(1+2x²)y=1-2x²
y+2yx²=1-2x²
(y+1)×2x²=1-y
2x²=(1-y)/(1+y)
因为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
　　祝学习快乐(1+y)(1-y)≥0且1+y≠-1 (1+y)(y-1)≤0且1+y≠-1是咋来的(1+y)(1-y)≥0且1+y≠-11-y变为y-1，多了一个负号，不等式方向要改变(1+y)(y-1)≤0且1+y≠-1(1-y)/(1+y)≥0到(1+y)(1-y)≥0且1+y≠-1咋来的不好意思，上面应该是(1+y)(1-y)≥0且1+y≠0(1-y)/(1+y)≥0两边同时乘以(1+y)²得到的，1+y≠0是分母不为0