1. ## factorise

$x^5+x^3+x$

I am not sure how to factorise the above equation as its constant term is 0 .

$x^5+x^3+x$
$=x(x^4+x^2+1)$
$x^4+x^2+1=x^4+2x^2+1-x^2=(x^2+1)^2-x^2$