Question

$(-x^{3}+12x+5)-(-x^{2}+5-9x^{3})$

Explanation:

Step1: Distribute the negative sign

$-x^3 + 12x + 5 + x^2 - 5 + 9x^3$

Step2: Combine like $x^3$ terms

$(-x^3 + 9x^3) + x^2 + 12x + (5 - 5)$
$=8x^3 + x^2 + 12x + (5 - 5)$

Step3: Combine constant terms

$8x^3 + x^2 + 12x + 0$

Answer:

$8x^3 + x^2 + 12x$