No, it is not correct. You calculator is right (assuming you meant In order that ab> 0, a and b must have the same sign, NOT just "a> 0, b> 0". That is, either a> 0 and b> 0 or a< 0, and b< 0. x> 0 and 1- x^2> 0 gives 0< x< 1. x< 0 and 1-x^2< 1 gives x^2> 0 which is true for any x< 0. Of course, x= 0 and x= 1 are also included.