Answer
$16x^{5}+26x^{3}-9x^{2}$
Work Step by Step
$3x^{2}(6x^{3}+2x-3)=(3x^{2})(6x^{3}) +(3x^{2})(2x)+(3x^{2})(-3)$
$=18x^{5}+6x^{3}-9x^{2}\qquad$ ... $(*)$
$-4x^{3}(x^{2}-5)=-4x^{3}(x^{2})-4x^{3}(-5)$
$=-4x^{5}+20x^{3}\qquad(**)$
Combine like terms of (*) and (**)
Problem=$(20x^{5}-4x^{5})+(6x^{3}+20x^{3})-9x^{2}$
=$16x^{5}+26x^{3}-9x^{2}$
