Explain the error in the work shown. Find the correct answer.

Answer:

The error is that the bases were not rewritten to be the same. Since 16 = 4^2, the right side is (4^2)^(2a) = 4^(4a), not 2^(8a) when comparing with 4^-3. Thus -3 = 4a and the correct solution is a = -3/4.