Question

这种不等式该怎么解 (a-1)/(a+1) 小于 1如果a+1乘过去 两边的a就没了

Answer 1

(a-1)/(a+1) < 1

=> (a+1 - 2)/(a+1) < 1

=> 1 - 2/(a+1) < 1

=> 1/(a+1) > 1

=> a+1 > 0 且 1 > a+1

=> -1 < a < 0