tolong bantu no.15 ya...

x/y - y/x dibagi 2y/x - 2x/y
=x^2 - y^2/xy dibagi 2y^2-2x^2/xy
=x^2 - y^2/xy kali xy/2y^2-2x^2
=x^2 - y^2/2y^2 - 2x^2
=(x+y)kali(x-y)
___________
(y+x)kali(y-x)kali2

= (x-y) per (y-x)kali2
= (x-y) per (x-y)kali -2
=- -1/2