Faà di Bruno's Formula/Example/2

Example of use of Faà di Bruno's Formula: $n = 2$
Consider Faà di Bruno's Formula:

When $n = 2$ we have:
 * $D_x^2 w = D_u^2 w \paren {D_x^1 u}^2 + D_u^1 w D_x^2 u$