> solve({Phi[1]-Phi[2]-a^2/6,-Phi[1]+4*Phi[2]-2*Phi[3]-a^2/3,-2*Phi[2]+4
> *Phi[3]-2*a^2/3}, {Phi[1], Phi[2], Phi[3]});

                         2              2              2
                      7 a            3 a            5 a
            {Phi[1] = ----, Phi[3] = ----, Phi[2] = ----}
                       12             8              12

> 
