(A= left( begin array lll (b+c)^2 & a^2 & b c (c+a)^2 & b^2 & c a (a+b)^2 & c^2 & a b end array right), B= left( begin array lll 1 & 0 & 1 0 & 2 & 0 3 & 0 & 1 end array right), C=

\mathrm{A}=\left(\begin{array}{lll}(b+c)^2 & a^2 & b c \\ (c+a)^2 & b^2 & c a \\ (a+b)^2 & c^2 & a b\end{array}\right), B=\left(\begin{array}{lll}1 & 0 & 1 \\ 0 & 2 & 0 \\ 3 & 0 & 1\end{array}\right), C=\left(\begin{array}{l}x \\ y \\ z\end{array}\right), D=\left(\begin{array}{l}1 \\ 2 \\ 1\end{array}\right)

MB 23RB 19

\mathrm{A}=\left(\begin{array}{lll}(b+c)^2 & a^2 & b c \\ (c+a)^2 & b^2 & c a \\ (a+b)^2 & c^2 & a b\end{array}\right), B=\left(\begin{array}{lll}1 & 0 & 1 \\ 0 & 2 & 0 \\ 3 & 0 & 1\end{array}\right), C=\left(\begin{array}{l}x \\ y \\ z\end{array}\right), D=\left(\begin{array}{l}1 \\ 2 \\ 1\end{array}\right)

MB 23RB 19

(A= left( begin array lll (b+c)^2 & a^2 & b c (c+a)^2 & b^2 & c a (a+b)^2 & c^2 & a b end array right), B= left( begin array lll 1 & 0 & 1 0 & 2 & 0 3 & 0 & 1 end array right), C= left( begin array l x y z end array right), D= left( begin array l 1 2 1 end array right) )