У+х y-z у+х y-z x*(y+x) +z*(y-z)
------------ + ----------- = ------------ + ----------- = ----------------------- =
z²+zx xz+x² z( z+x) x(z+x) xz(z+x)
xy+x²+zy-z² (xy+zy)+(x²-z²) y(x+z)+(x+z)(x-z)
= --------------------- = ------------------------- = -------------------------- =
xz(z+x) xz(z+x) xz(z+x)
(x+z)(y+x-z) y+x-z
= ------------------- = -------------------
xz(z+x) xz