Question

X³-{4X²-X-[-2X²-(5X²-X)-8X]-5X²}

Answer 1

$x^3-\{4x^2-x-[-2x^2-(5x^2-x)-8x]-5x^2\} \to\\\\ x^3-\{4x^2-x-[-2x^2-5x^2+x-8x]-5x^2\} \to\\\\ x^3-\{4x^2-x-[-7x^2-7x]-5x^2\} \to\\\\ x^3-\{4x^2-x+7x^2+7x-5x^2\} \to\\\\ x^3-\{6x^2+6x\} \to\\\\ \large\boxed{x^3-6x^2-6x}$