Answer
$=5x(x^{2}+1)^{4}(x^{3}+1)^{4}(5x^{3}+3x+2)$
Work Step by Step
$10x(x^{2}+1)^{4}(x^{3}+1)^{5}+15x^{2}(x^{2}+1)^{5}(x^{3}+1)^{4}$
$=5x(x^{2}+1)^{4}(x^{3}+1)^{4}[2(x^{3}+1)+3x(x^{2}+1)]$
$=5x(x^{2}+1)^{4}(x^{3}+1)^{4}(2x^{3}+2+3x^{3}+3x)$
$=5x(x^{2}+1)^{4}(x^{3}+1)^{4}(5x^{3}+3x+2)$