Extract the required roots of the following expressions:

1. Find the square root of \(16a^4b^6\)
2. Find the cube root of \(-27x^3y^9\)
3. Find the square root of the polynomial: \(x^2 + 6x + 9\)
4. Find the square root of: \(a^4 - 4a^2b + 4b^2\)
5. Extract the fourth root of \(81m^8n^{12}\)