If log8 m + log8 1/6 = 2/3, then m is equal to

2025

If log8 m + log8 1/6 = 2/3, then m is equal to

  1. A.

    24

  2. B.

    18

  3. C.

    12

  4. D.

    4

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Show answer & explanation

Correct answer: A

Concept: For logarithms with the same base, the product rule states loga(m) + loga(n) = loga(mn). Also, by the definition of a logarithm, logx(y) = a means y = xa — converting a log equation into an exponential one lets us solve for the unknown directly.

Application:

  1. Combine the two logarithmic terms on the left using the product rule: log8(m) + log8(1/6) = log8(m × 1/6) = log8(m/6).

  2. The equation becomes log8(m/6) = 2/3.

  3. Convert to exponential form using the definition of a logarithm: m/6 = 82/3.

  4. Rewrite 8 as 23 and simplify the exponent: 82/3 = (23)2/3 = 22.

  5. So m/6 = 22, and solving for m gives m = 6 × 22 = 24.

Cross-check: Substitute m = 24 into the original left-hand side: log8(24) + log8(1/6) = log8(24 × 1/6) = log8(4). Writing both numbers as powers of 2 (8 = 23, 4 = 22) and using the power rule, log8(4) = 2/3 — exactly matching the right-hand side, which confirms the value of m.

∴ m = 24.

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