✔ 最佳答案
.............................
|x|<1,-l< (x-y)/(1-xy) <1,試求y的範圍?
Sol
|x|<1
-1<x<1
0<x+1,x-1<0
-l< (x-y)/(1-xy)
(x-y)/(1-xy)+1>0
(x-y+1-xy)/(1-xy)>0
(x-y+1-xy)(1-xy)>0
[(x+1)-y(1+x)](1-xy)>0
(1+x)(1-y)(1-xy)>0
1+x>0
(1-y)(1-xy)>0……………
(x-y)/(1-xy)<1
(x-y)/(1-xy)-1<0
(x-y-1+xy)/(1-xy)<0
(x-y-1+xy)(1-xy)<0
[(x+xy)-(y+1)](1-xy)<0
(x-1)(y+1)(1-xy)<0
x-1<0
(y+1)(1-xy)>0…………..
(1-y)(1-xy)(y+1)(1-xy)>0
(1-y)(1+y)(1-xy)^2>0
(1-y)(1+y)>0
-1<y<1