Giúp mk bài 5,6 vs ạ. Mk cảm ơn

bài 5:
$\displaystyle  \begin{array}{{>{\displaystyle}l}}
a,x^{3} +1=( x+1)\left( x^{2} -x+1\right)\\
b,x^{3} -\frac{1}{27} =\left( x-\frac{1}{3}\right)\left( x^{2} +\frac{2x}{3} +\frac{1}{9}\right)\\
c,x^{3} -27y^{3} =( x-3y)\left( x^{2} +6xy+9y^{2}\right)
\end{array}$
bài 6:
$\displaystyle  \begin{array}{{>{\displaystyle}l}}
a,A=( x+2)\left( x^{2} -2x+4\right) -x^{3} +2\\
\Rightarrow A=x^{3} +8-x^{3} +2=10
\end{array}$