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Find the exact value of log base 2 of one sixteenth.
AIt equals 4
BIt equals -4
CIt equals -8
DIt equals -16
Answer & Solution
Correct answer: B. It equals -4
1. Set the logarithm equal to x, so log base 2 of one sixteenth equals x.
2. Convert to exponential form, giving 2 to the power x equal to one sixteenth.
3. Rewrite 16 as a power of 2 by doubling: 2, 4, 8, 16.
4. That takes four doublings, so 16 is 2 to the fourth.
5. A reciprocal flips the sign of the exponent, so one sixteenth is 2 to the power negative 4.
6. With the bases matching, the exponents must be equal, so x is negative 4.
7. Answering 4 ignores that the argument is a reciprocal rather than 16 itself.
8. Answering negative 8 doubles the exponent instead of counting the doublings.
9. Answering negative 16 reports the argument rather than the exponent.
_Source: OpenStax Intermediate Algebra (CC BY 4.0), section 10.3 Evaluate and Graph Logarithmic Functions_