Final answer:
The coefficient of x^3 in the expansion (3x^3 + 4x) (2x^2 + 5) is 6.
Step-by-step explanation:
In the expansion of (3x^3 + 4x) (2x^2 + 5), we need to find the coefficient of x^3.
To find the coefficient, we need to multiply the terms that have x^3 in both the expressions and add them together.
The terms that have x^3 are (3x^3) and (2x^2). When we multiply these terms, we get (3x^3) * (2x^2) = 6x^5.
Therefore, the coefficient of x^3 in the expansion is 6.