Đáp án:
$\begin{array}{l}
Do:{x^3} + {y^3} = {\left( {x + y} \right)^3} - 3x.y.\left( {x + y} \right)\\
B = {\left( {a + b - 2c} \right)^3} + {\left( {b + c - 2a} \right)^3} + {\left( {c - a - 2b} \right)^3}\\
= {\left( {a + b - 2c + b + c - 2a} \right)^3} - 3.\left( {a + b - 2c} \right).\left( {b + c - 2a} \right).\\
\left( {a + b - 2c + b + c - 2a} \right) + {\left( {c - a - 2b} \right)^3}\\
= {\left( {2b - a - c} \right)^3} - {\left( {2b - a - c} \right)^3} - 3.\left( {a + b - 2c} \right).\left( {b + c - 2a} \right).\\
\left( {2b - a - c} \right)\\
= - 3.\left( {a + b - 2c} \right).\left( {b + c - 2a} \right).\left( {2b - a - c} \right)\\
= 3.\left( {a + b - 2c} \right).\left( {b + c - 2a} \right).\left( {a + c - 2b} \right)
\end{array}$
