Solve 1/log₄(9): Simplifying Reciprocal Logarithm Expression

Reciprocal Logarithm Property with Base Change

1log49= \frac{1}{\log_49}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:04 We'll use the formula for dividing 1 by log
00:10 We'll get a log with inverse base and number
00:13 We'll use this formula in our exercise
00:17 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

1log49= \frac{1}{\log_49}=

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Identify the property of logarithms that relates inverses.
  • Step 2: Apply this property to the given expression.
  • Step 3: Compare with provided choices to identify the correct option.

Now, let's work through each step:

Step 1: The problem asks us to find the expression equal to 1log49\frac{1}{\log_4 9}.

Step 2: We use the logarithmic property logba=1logab\log_b a = \frac{1}{\log_a b}. Thus, replacing b b with 9 and a a with 4, we have:

1log49=log94\frac{1}{\log_4 9} = \log_9 4.

Step 3: Comparing this result to the provided choices, we find that the correct answer is log94\log_9 4, corresponding to Choice 1.

Therefore, the solution to the problem is log94\log_9 4.

3

Final Answer

log94 \log_94

Key Points to Remember

Essential concepts to master this topic
  • Property: The reciprocal of a logarithm equals the base-swapped logarithm
  • Technique: 1log49=log94 \frac{1}{\log_4 9} = \log_9 4 by swapping base and argument
  • Check: Verify both expressions equal same decimal value using calculator ✓

Common Mistakes

Avoid these frequent errors
  • Confusing reciprocal with negative logarithm
    Don't write 1log49=log49 \frac{1}{\log_4 9} = -\log_4 9 = wrong answer! The reciprocal property swaps base and argument, it doesn't make the logarithm negative. Always remember 1logba=logab \frac{1}{\log_b a} = \log_a b .

Practice Quiz

Test your knowledge with interactive questions

\( \log_{10}3+\log_{10}4= \)

FAQ

Everything you need to know about this question

Why does 1log49 \frac{1}{\log_4 9} equal log94 \log_9 4 ?

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This is the reciprocal logarithm property! When you take the reciprocal of a logarithm, you simply swap the base and the argument. So 1log49=log94 \frac{1}{\log_4 9} = \log_9 4 .

How can I remember this property?

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Think of it as "flip the fraction, flip the positions". When you flip 1log49 \frac{1}{\log_4 9} to get rid of the fraction, the 4 and 9 also flip positions!

Is this the same as the change of base formula?

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Yes! The change of base formula is logba=logalogb \log_b a = \frac{\log a}{\log b} . The reciprocal property is a special case where we use 1logba=logbloga=logab \frac{1}{\log_b a} = \frac{\log b}{\log a} = \log_a b .

What if I chose log419 \log_4 \frac{1}{9} instead?

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That's a different property! log419=log49 \log_4 \frac{1}{9} = -\log_4 9 uses the negative exponent rule, not the reciprocal property. Always check which operation you're dealing with.

Can I verify this answer is correct?

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Absolutely! Calculate both 1log49 \frac{1}{\log_4 9} and log94 \log_9 4 using a calculator. Both should give you approximately 0.631, confirming they're equal!

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