Câu trong ảnh làm như nào các bạn ơi...

$\displaystyle  \begin{array}{{>{\displaystyle}l}}
5A.\\
a) \ ( x+1)\left( x^{2} -x+1\right) -( x+3)\left( x^{2} -3x+9\right)\\
=x^{3} +1-\left( x^{3} +27\right)\\
=1-27\\
=-26\\
b) \ ( y+2)\left( y^{2} -2y+4\right) +( 5-y)\left( 25+5y+y^{2}\right)\\
=y^{3} +8+125-y^{3}\\
=133\ 
\end{array}$

5B.
$\displaystyle  \begin{array}{{>{\displaystyle}l}}
a) \ ( x+2)\left( x^{2} -2x+4\right) -( 1-3x)\left( 1+3x+9x^{2}\right)\\
=x^{3} +8-\left( 1-27x^{3}\right)\\
=x^{3} +8-1+27x^{3}\\
=28x^{3} +7\\
b) \ ( x+y)\left( x^{2} -xy+y^{2}\right) +( 2y-x)\left( x^{2} +2xy+4y^{2}\right)\\
=x^{3} +y^{3} +8y^{3} -x^{3}\\
=9y^{3} \ 
\end{array}$