> solve({4*c[1]+6*l*c[2]+8*l^2*c[3]=Fl/EI,
> 6*c[1]+12*l*c[2]+18*l^2*c[3]=Fl/EI,                                  
> 8*c[1]+18*l*c[2]+(144/5)*l^2*c[3]=Fl/EI}, {c[1],c[2],c[3]});

                                     Fl            Fl
               {c[3] = 0, c[2] = - ------, c[1] = ----}
                                   6 l EI         2 EI

> 
