Question

Factorise the following trinomials:
$81+18x+x^2$

Answer 1

$81+18x+x^2$

$=x^2+18x+81$

$=x^2+9x+9x+81$

$=x(x+9)+9(x+9)$

$=(x+9)(x+9)$

Hence the factors of $81+18x+x^2$ are $(x+9)$ and $(x+9)$.