$$$This is a factorisation that you need to memorise$\\\\ \boxed{a^3\pm b^3=(a\pm b)(a^2\mp ab+b^2)}\\\\ so\\ 1+27x^3\\ =1^3+(3x)^3\\ =(1+3x)(1-3x+9x^2)$$
$$$This is a factorisation that you need to memorise$\\\\ \boxed{a^3\pm b^3=(a\pm b)(a^2\mp ab+b^2)}\\\\ so\\ 1+27x^3\\ =1^3+(3x)^3\\ =(1+3x)(1-3x+9x^2)$$
