∂u/∂x=[∂u/∂(xy)][d(xy)/dx]+[∂u/∂(x/y)][d(x/y)/dx]=yf₁'+(1/y)f₂'∂u/∂y=[∂u/∂(xy)][d(xy)/dy]+[∂u/∂(x/y)][d(x/y)/dy]=xf&...