\(U= log(x+2y+3z)\)
»\(y=logx
\)
»\( dy = {1\over x}\)
\({dU\over dx} = {1\over (x+2y+3z)}.{d\over dx}(x+2y+3z)\)
⇒\({dU\over dx} = {1\over (x+2y+3z)}\)
\({dU\over dy} = {1\over (x+2y+3z)}.{d\over dy}(x+2y+3z)\)
⇒\({dU\over dy} = {2\over (x+2y+3z)}\)
\({dU\over dz} = {1\over (x+2y+3z)}.{d\over dz}(x+2y+3z)\)
⇒\({dU\over dz} = {3\over (x+2y+3z)}\)