Simplify (-8y^2-9y)-(-8y^3+9y^2-5y)

$(- 8 y^{2} - 9 y) - (- 8 y^{3} + 9 y^{2} - 5 y)$

Simplify each term.

Apply the distributive property.

$- 8 y^{2} - 9 y - (- 8 y^{3}) - (9 y^{2}) - (- 5 y)$

Simplify.

Multiply $- 8$ by $- 1$ .

$- 8 y^{2} - 9 y + 8 y^{3} - (9 y^{2}) - (- 5 y)$

Multiply $9$ by $- 1$ .

$- 8 y^{2} - 9 y + 8 y^{3} - 9 y^{2} - (- 5 y)$

Multiply $- 5$ by $- 1$ .

$- 8 y^{2} - 9 y + 8 y^{3} - 9 y^{2} + 5 y$

Simplify by adding terms.

Subtract $9 y^{2}$ from $- 8 y^{2}$ .

$- 17 y^{2} - 9 y + 8 y^{3} + 5 y$

Add $- 9 y$ and $5 y$ .

$- 17 y^{2} + 8 y^{3} - 4 y$

Reorder $- 17 y^{2}$ and $8 y^{3}$ .

$8 y^{3} - 17 y^{2} - 4 y$