Is it possible to solve integration with derivatives and unknown functions inside the integral... I am trying to solve the integral > int((diff(a(x),x,x))*(diff(u[1](x),x,x,x,x))*u[2](x)+((u[1](x))*(u[2](x)))*b(x),x=0..L); where u[1](x), u[2](x), a(x), and b(x) are unknown functions of x, and it keeps giving me back the integral... Is it possible...