Simplify 2a^2b^3 (4a^2+3ab^2-ab)

2a^2b^3 (4a^2+3ab^2-ab) = ?

is what I presume you actually meant.

Pull out the common factors of (4a^2+3ab^2-ab) and you will get

a (4a+3b^2 - b)

Substitute this back into the original equation and you get

2a^2b^3[a (4a+3b^2-b) ] =

2a^3b^3 (4a+3b^2-b) =

2a^3b^3 (4a-b+3b^2)