Question 615622
The first step in factoring a polynomial is "taking out the common factor" (if there is one).
Since {{{21x^6=(3x^2)*(7x^4)}}} and {{{18x^2=(3x^2)*6}}}
you can take out {{{3x^2}}} as a common factor:
{{{21x^6+18x^2=(3x^2)*(7x^4)+(3x^2)*6=highlight((3x^2)*(7x^4+6))}}}
There is no way you can factor {{{7x^4+6}}}, so the factoring is complete.