Equation Icon  ∫ 1 2 ∫ 1( )2 ∫ 1 2 ∂-uN-(x ,t)u (x ,t)w (x)dx = ∂uN-- w (x)dx − 1- u2 ∂-w-dx. (163 ) −1 ∂x2 k N k −1 ∂x 2 −1 N∂x2