I wаnt tо use Cаstigliаnо's methоd to find the deflection in this simply supported beam due to P at a point 1 meter away from O. I write the energy E = integral of M(x)^2 / 2EI from x= 0 to x =6. Here, M(x) is the moment due to P and support reactions at some point x m from O. Then, the deflection at x =1 is: