Simplify (3x^3+6x^2-18x)+(4x^2-24x+8)

$(3 x^{3} + 6 x^{2} - 18 x) + (4 x^{2} - 24 x + 8)$

Remove parentheses.

$3 x^{3} + 6 x^{2} - 18 x + 4 x^{2} - 24 x + 8$

Add $6 x^{2}$ and $4 x^{2}$ .

$3 x^{3} + 10 x^{2} - 18 x - 24 x + 8$

Subtract $24 x$ from $- 18 x$ .

$3 x^{3} + 10 x^{2} - 42 x + 8$