Variables:
Example
Example 1:| $Aa^3-8 &= a^3-2^3=\\ &=(a-2)(a^2+a\cdot2+2^2)=\\ &= (a-2)(a^2+2a+4)A$ | Example 2:| $A 27x^3-1 &= (3x)^3-1^3=\\ &= (3x-1)((3x)^2+3x\cdot1 +1^2)\\ &= (3x-1)(9x^2+3x+1) A$
$$\begin{aligned}(a-1)^4 =&a^4-4a^3\cdot1+6a^2\cdot1^2-4a\cdot1^3+1^4\\[1.2em] =&a^4-4a^3-4a+1\end{aligned}$$