Use the binomial theorem to expand expressions 1-4 and answer question 5.

1. (3x^2 +y)^3
2. (5x^4 +2y^5)^4
3. (x^3 +4y^2)^5
4. (x-2y)^6
5. find the coefficient of x^3 y^4 in the expansion of (2x+5y^2)^5