A-x b+x a-x+b+x a+b
----- +------- = ------------- = ------------
m m m m
ax-y y+bx ax-y+y+bx x(a+b)
------- + ---------- = ------------------ = ------------- =x
a+b a+b a+b a+b
px-3q py-3q px-3q py-3q px-3q - py+3q p(x-y)
-------- + ------------ = --------- - ------------ = --------------------- =------------ = p
x-y y-x x-y x-y x-y x-y