In Exercises 21–42, evaluate each expression without using a calculator. log2 (1/8)

Logarithms are the inverse operations of exponentiation. The logarithm log_b(a) answers the question: 'To what exponent must the base b be raised to produce a?' For example, log_2(8) = 3 because 2^3 = 8. Understanding logarithms is essential for evaluating expressions like log_2(1/8).

The Change of Base Formula allows you to convert logarithms from one base to another, which can simplify calculations. It states that log_b(a) = log_k(a) / log_k(b) for any positive k. This is particularly useful when dealing with logarithms that are not easily computed in their original base.

Negative exponents represent the reciprocal of the base raised to the absolute value of the exponent. For instance, a^(-n) = 1/(a^n). In the context of logarithms, recognizing that 1/8 can be expressed as 2^(-3) helps in evaluating log_2(1/8) by transforming the expression into a more manageable form.