题目应是　已知y=x的平方-1分之x的平方-2x+1除以x+1分之x的平方-x乘以5x,试说明在代数式有意义的情况下,不论x取何值,y的值都不变
y=(x^2-2x+1)/(x^2-1) ÷ (x^2-x)/(x+1) *5x
y=(x-1)^2/(x+1)(x-1) * (x+1)/x(x-1) *5x
y=(x-1)/(x+1) * (x+1)/x(x-1) *5x
y=5
所以不论x取何值,y的值都不变