Choose the correct simplification of the expression b5 ⋅ b4. b b9 b20 b-1

When multiplying like terms, you add the exponents:

b^5 · b^4 = b^ (5+4) = b^9

FYI - when dividing like terms, subtract the exponents.

The only time we multiply exponents is when they distribute across parentheses:

(x³) ² = x^6