Question

Factorise
1 – 27a³

Answer 1

$$\begin{gathered} 1-27a^3=1^3-{\left(3a\right)}^3 \\ =\left(1-3a\right)\left[1^2+1\times 3x+{\left(3a\right)}^2\right] \\ =\left(1-3a\right)\left(1+3a+9a^2\right) \end{gathered}$$