Solving symbolically a system of equations with boundary values

Hello, I´m new to Mathcad Prime 3 and haven't find a solutión on internet or here

What I´m trying to do is to solve simbolically g ‘ ‘ (x) = M where M =P2*x-P3

The answer should be, P2 = 12 EI/L^3, P3 = 6 EI/L^2, c2 = 1, and c1 = 0.

g ' (x) = (P2*x^2)/2 - P3*x + c1

Then solving for g ’ (x=0) = 0 wich gives me c1=0 and solving for g ’ (x=L) = 0 wich gives me P3 = P2*L/2

g (x) = (P2*x^3)/6 - (P3*x^2)/2 + c1*x + c2

Then replacing P3 in g (x), solving for g (x=0) = 1 wich gives me c2=1 and solving for g (x=L) = 0 wich gives me P2 = 12 EI/L^3

Is there a way that Mathcad do this with find function? or something else that is like placing equations, then placing boundary value conditios and get an answer?

I attach a sheet with averything i have tried

thanks.

JAC