Đáp án:
Giải thích các bước giải:
\(\begin{array}{l}{(a + b)^3} - {(a - b)^3} = \left[ {\left( {a + b} \right) - \left( {a - b} \right)} \right]\left[ {{{\left( {a + b} \right)}^2} + \left( {a + b} \right)\left( {a - b} \right) + {{\left( {a - b} \right)}^2}} \right]\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \,\,\,\,2b.\left[ {{a^2} + 2ab + {b^2} + {a^2} - {b^2} + {a^2} - 2ab + {b^2}} \right]\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \,\,\,\,\,2b.\,\left( {3{a^2} + {b^2}} \right)\end{array}\)
