Nomor 4 yang A-B dong sama caranya. besok dikumpulin..

Jawabannya dilampiran yah
Maaf kalau salah

a) ( x - y )/ (x^-1 + y^-1)
= (x - y) / ( 1/x + 1/y)
= (x - y) / { (x + y)/xy }
= xy (x - y)/(x + y)
b) (x^-2 - y^-2) / (x^-1 - y^-1)
= (x^-1)^2 - (y^-1)^2 / (x^-1 - y^-1)
= (x^-1 + y^-1)(x^-1 - y^-1)/(x^-1 - y^-1)
= (x^-1 + y^-1)
= 1/x + 1/y
c) xy^-1 - x^-1y / x^-1 - y^-1
= (x/y - y/x) / (1/x - 1/y)
= { (x^2 - y^2)/xy } / { (y - x)/xy }
= (x^2 - y^2) / (y - x)
= (x + y)(x - y) / -(x - y)
= - (x + y)
= -x - y