Question 12939
{{{10x^4+21x^2+9}}}
={{{10x^4+6x^2+15x^2+9}}}
={{{(2x^2*5x^2+3*2x^2)+(3*5x^2+3*3)}}}
={{{((highlight(2x^2))*5x^2+3*(highlight(2x^2)))+((highlight(3))*5x^2+(highlight(3))*3)}}}
={{{(2x^2(5x^2+3))+(3(5x^2+3))}}}
={{{(2x^2(highlight((5x^2+3))))+3(highlight((5x^2+3))))}}}
={{{(2x^2+3)(5x^2+3)}}}

OK