What is the highest degree of the polynomial function

f(x) = 7b^3(3b+3)

The highest degree of the polynomial function is 4.

The polynomial function f(x) can be expanded as:
f(x) = 7b^3(3b) + 7b^3(3)
f(x) = 21b^4 + 21b^3

The highest degree term in the expanded form of the polynomial function is b^4, which means the highest degree of the polynomial function f(x) is 4.