Answer
$6x(x^{3}+7)(-2x^{3}-5x+7)$
Work Step by Step
$6x(x^{3}+7)^{2}-6x^{2}(3x^{2}+5)(x^{3}+7)$
greatest common factor=$6x(x^{3}+7)$
$=[6x(x^{3}+7)]\cdot(x^{3}+7)-[6x(x^{3}+7)]\cdot x(3x^{2}+5)$
$=6x(x^{3}+7)[(x^{3}+7)-x(3x^{2}+5)]$
$...$ simplify the expression in brackets
$=6x(x^{3}+7)(x^{3}+7-3x^{3}-5x)$
$=6x(x^{3}+7)(-2x^{3}-5x+7)$
