Let $w = x y z$ $x = s + t$

Short Answer

Let $w = x y z$ , $x = s + t$ , $y = s ^ { 2 } - t ^ { 2 }$ and $z = s t$ . Use the chain rule to show that $s \left( \frac { \delta w } { \delta s } \right) + t \left( \frac { \delta w } { \delta t } \right) = 5 x y z$ .