> with(linalg):
> K[red]:=(1/1680)*matrix(5,5,[[2524,-3303,3366,3366,-3303],[-3303,10665
> ,-11043,-6804,3969],[3366,-11043,16335,9639,-6804],[3366,-6804,9639,16
> 335,-11043],[-3303,3969,-6804,-11043,10665]]);

                    [ 2524     -3303      3366      3366     -3303]
                    [                                             ]
                    [-3303     10665    -11043     -6804      3969]
                    [                                             ]
   K[red] := 1/1680 [ 3366    -11043     16335      9639     -6804]
                    [                                             ]
                    [ 3366     -6804      9639     16335    -11043]
                    [                                             ]
                    [-3303      3969     -6804    -11043     10665]

> F:=(1/8)*a^2*vector([2,-3,9,9,-3]);

                              2
                    F := 1/8 a  [2, -3, 9, 9, -3]

> Phi:=linsolve(K[red],F);

             [     2          2         2         2          2]
             [650 a   141130 a   95900 a   95900 a   141130 a ]
      Phi := [------, ---------, --------, --------, ---------]
             [ 1097    266571     266571    266571    266571  ]

> 
