x*(y-z)-y*(x+r)-r*(x-y)
xy-xz-y*(x+r)-r*(x-y)
xy-xz-xy-ry-r*(x-y)
xy-xz-xy-ry-rx+ry
-xz-ry-rx+ry
-xz-rx
x*(y-z)-y*(x+r)-r*(x-y)
xy-xz-y*(x+r)-r*(x-y)
xy-xz-xy-ry-r*(x-y)
xy-xz-xy-ry-rx+ry
-xz-ry-rx+ry
-xz-rx