If log(x + 4) = log(4) + log(x) and log(y + 6) = log(6), compare x and y.

Difficulty: Easy

Correct Answer: x > y

Explanation:


Introduction / Context:
We solve two simple log equations independently and then compare the resulting values of x and y. The base is common (10 by default) and positivity of arguments must be ensured.


Given Data / Assumptions:

  • log(x + 4) = log(4) + log(x) = log(4x).
  • log(y + 6) = log(6).
  • All log arguments are positive.


Concept / Approach:

  • Use logarithm properties: log A + log B = log(AB).
  • Since log is one-to-one on positive reals, equate arguments.


Step-by-Step Solution:

x + 4 = 4x ⇒ 3x = 4 ⇒ x = 4/3 ≈ 1.333…y + 6 = 6 ⇒ y = 0Compare: x ≈ 1.333… > y = 0 ⇒ x > y.


Verification / Alternative check:
Domain check: x + 4 > 0 and x > 0 (true for x = 4/3). For y, y + 6 > 0 (true for y = 0).


Why Other Options Are Wrong:

  • x = y or x < y contradict the computed values.
  • “Can’t say” is incorrect; both equations uniquely determine x and y.


Common Pitfalls:

  • Using log(a) + log(b) = log(a + b), which is false.


Final Answer:
x > y

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