帮下忙,[x]帮下忙,[x]
帮下忙,[x]先不妨设x>y.(因为外面都有绝对值,所以x,y地位平等,所以可以这样设).那么|x-y/1-xy |-1 = (x-y-1+xy)/(1-xy) = (x-1)(1-y)/(1-xy)