Question

当分式x+1分之x-1的值为负数,正数,零时,求x的取值范围

Answer 1

(x-1)/(x+1)＜0

(x-1)(x+1)＜0 (左右同时乘以(x+1)^2)

x∈(-1,1)

(x-1)/(x+1)=0

x=1

(x-1)/(x+1)＞0

(x-1)(x+1)＞0 (左右同时乘以(x+1)^2)

x∈(-∞,-1)∪(1,+∞)