Re: how do i prove whether a number is an integer?
Originally Posted by creation1022
in the same way that I can make X a negative;
Or make X a positive; X>0
Writing x < 0 does not make x negative or change x in any way. Rather, for each value of x, the formula x < 0 is true or false. As far as notation goes, you can write or just write "x is an integer"; this statement would be true iff x is an integer. If you need to express the property of being an integer using other concepts, then the answer depends on what you are allowed to use. For example, if you are working with rational numbers and are allowed to use the ceiling function , then x is an integer iff . In the context of set theory see Plato's response.