[tex]\displaystyle\bf\\a) \overline{xx} + \overline{yy} + \overline{zz}= 11x+11y+11z=11(x+y+z)=\mathcal{M}_{11}.\\b) \overline{xy} + \overline{yz} + \overline{zx} = (10x+y)+(10y+z)+(10z+x)=11x+11y+11z=\\11(x+y+z)=\mathcal{M}_{11}.\\c) \overline{xz}+\overline{zy}+\overline{yx}=(10x+z)+(10z+y)+(10y+x)=11x+11y+11=11(x+y+z)=\mathcal{M}_{11}.[/tex]
