Answer :
there are few ways to write this down :)
[tex](-1)^x[/tex]
where x is even positive number
or
[tex](-1)*(-y)[/tex]
where y is negative number :)
[tex](-1)^x[/tex]
where x is even positive number
or
[tex](-1)*(-y)[/tex]
where y is negative number :)