Simplify 4x^3+9 (2x^3-5b^5

Well I assume that you mean 4x^3+9 (2x^3-5b^5) all within a parentheses and if that is the case then to solve this your would do the following.

Write down the equation

4x^3+9 (2x^3-5b^5)

Distribute

4x^3+18x^3-45b^5

Combine like terms

22x^3-45b^5

And because there are no more like terms that is your end answer

Enjoy!=)

It could be either ...

(4x³ + 9) (2x³ - 5b⁵)

8x⁶ - 20bx⁸ + 18x³ - 45b⁵

... or ...

4x³ + 9 (2x³ - 5b⁵)

4x³ + 9 (2x³) - 9 (5b⁵)

4x³ + 18x³ - 45b⁵

22x³ - 45b⁵

... either way, one of it could be the right answer.