Solve the Inverse Logarithm: Finding (log₇x)⁻¹

Inverse Logarithm with Base-Argument Exchange

(log7x)1= (\log_7x)^{-1}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:05 Let's solve a math problem together!
00:09 We'll use a formula to change a negative power into a fraction.
00:14 Now, let's apply this formula in our exercise.
00:21 Next, we'll divide 1 by the logarithm. Let's follow the formula.
00:26 Remember to switch the number and base for the logarithm.
00:31 We'll use this rule in our practice problem.
00:35 And that's how we find the solution to this question!

Step-by-step written solution

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1

Understand the problem

(log7x)1= (\log_7x)^{-1}=

2

Step-by-step solution

To solve this problem, we must determine the reciprocal of the logarithm expression log7x \log_7 x . This involves finding the inverse using the properties of logarithms.

  • Step 1: Recognize that the expression (log7x)1 (\log_7 x)^{-1} is asking for the reciprocal of the logarithm.
  • Step 2: Apply the inverse property of logarithms: (logba)1=logab(\log_b a)^{-1} = \log_a b.

Applying this property to our problem, we set b=7b = 7 and a=xa = x. Therefore, (log7x)1(\log_7 x)^{-1} transforms to:

logx7 \log_x 7

Thus, the value of the expression (log7x)1 (\log_7 x)^{-1} is logx7 \log_x 7 .

Therefore, the solution to the problem is logx7 \log_x 7 .

3

Final Answer

logx7 \log_x7

Key Points to Remember

Essential concepts to master this topic
  • Inverse Property: (logba)1=logab (\log_b a)^{-1} = \log_a b swaps base and argument
  • Technique: Transform (log7x)1 (\log_7 x)^{-1} by switching 7 and x positions
  • Check: Verify logx7log7x=1 \log_x 7 \cdot \log_7 x = 1 using change of base ✓

Common Mistakes

Avoid these frequent errors
  • Taking reciprocal of each part separately
    Don't write (log7x)1=log71x1=log1/7(1/x) (\log_7 x)^{-1} = \log_{7^{-1}} x^{-1} = \log_{1/7} (1/x) ! This treats the logarithm as a fraction when it's actually a single value. Always apply the inverse logarithm property: swap the base and argument positions.

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 the base and argument switch places?

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The inverse logarithm property comes from the definition of logarithms. If log7x=y \log_7 x = y , then 7y=x 7^y = x . The inverse asks: what power do we raise x to get 7? That's exactly logx7 \log_x 7 !

Is this the same as finding 1/log₇x?

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No! The notation (log7x)1 (\log_7 x)^{-1} means the inverse function, not the reciprocal. If you wanted the reciprocal, you'd write 1log7x \frac{1}{\log_7 x} , which is completely different.

How can I remember this property?

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Think of it as a "position swap": whatever is the base becomes the argument, and whatever is the argument becomes the base. Base and argument trade places!

Does this work with any logarithm base?

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Yes! The property (logba)1=logab (\log_b a)^{-1} = \log_a b works for any valid base (positive, not equal to 1) and any positive argument.

Can I check my answer using a calculator?

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Yes! Use the change of base formula: logx7=ln7lnx \log_x 7 = \frac{\ln 7}{\ln x} . Multiply this by log7x=lnxln7 \log_7 x = \frac{\ln x}{\ln 7} and you should get 1.

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