$$(f\circ f)(x,y,z)=f(f(x,y,z))=f(-y+z,-x+z,-x+y)$$
$$=$$
$$\left(-(-x+z)+(-x+y),-(-y+z)+(-x+y),-(-y+z)+(-x+z)\right)$$
$$=$$
$$\left(x-z-x+y,y-z-x+y,y-z-x+z\right)$$
$$=$$
$$\left(-z+y,2y-z-x,y-x\right)$$
O halde $$(f\circ f)(1,3,5)=\ldots$$ bulunur.