# Exercici 10.19

kill(all)$

g(x,y):=x+a*y;

z(x,y):=f(g(x,y));

Dxz(x,y) = diff(z(x,y), x);
Dyz(x,y) = diff(z(x,y), y);

Dxg = diff(g(x,y),x);
Dyg = diff(g(x,y),y);

Dxz(x,y) = Df(g(x,y)) * diff(g(x,y),x);
Dyz(x,y) = Df(g(x,y)) * diff(g(x,y),y);