Solve for x in the base-4 logarithmic equation: 2·log₄(x) = 1 + log₄(x − 1). State domain conditions and the final solution.

Difficulty: Medium

Correct Answer: 2

Explanation:


Introduction / Context:
We solve a logarithmic equation involving base 4 by converting the left-hand side with the power rule and equating arguments after combining using log identities.


Given Data / Assumptions:

  • Equation: 2·log₄(x) = 1 + log₄(x − 1)
  • Domain: x > 0 and x − 1 > 0 ⇒ x > 1


Concept / Approach:
Use 2·log₄ x = log₄(x^2) and 1 = log₄ 4. Then sum on the right: log₄ 4 + log₄(x − 1) = log₄(4(x − 1)). Equate arguments of equal logs.


Step-by-Step Solution:

Left: 2·log₄ x = log₄(x^2)Right: 1 + log₄(x − 1) = log₄ 4 + log₄(x − 1) = log₄(4(x − 1))Therefore x^2 = 4(x − 1)x^2 − 4x + 4 = 0 ⇒ (x − 2)^2 = 0 ⇒ x = 2


Verification / Alternative check:
Check domain: x = 2 > 1; substitute: 2·log₄ 2 = 2·(1/2) = 1; right side 1 + log₄ 1 = 1 + 0 = 1. Holds exactly.


Why Other Options Are Wrong:
1 violates the domain; 3 and 4 do not satisfy the quadratic; “no real solution” is incorrect since x = 2 is valid.


Common Pitfalls:
Forgetting to use log₄ 4 = 1 or mishandling the power rule can lead to an incorrect linear equation instead of the correct quadratic.


Final Answer:
2

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