Solve Complex Fraction: 2x/(log₈9) ÷ log₉8 Simplification

Logarithmic Properties with Multiplicative Inverses

2xlog89log98= \frac{\frac{2x}{\log_89}}{\log_98}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:04 Let's break down the multiplication from the fraction
00:14 We'll use the formula of dividing 1 by log
00:17 We'll get the log of the inverse number and base
00:27 We'll use this formula in our exercise
00:40 Let's reduce what we can
00:44 And this is the solution to the question

Step-by-step written solution

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1

Understand the problem

2xlog89log98= \frac{\frac{2x}{\log_89}}{\log_98}=

2

Step-by-step solution

To solve this problem, we will simplify the expression 2xlog89log98\frac{\frac{2x}{\log_8 9}}{\log_9 8}.

Step 1: Apply the inverse log property.

The property logba×logab=1\log_b a \times \log_a b = 1 states that these logs are multiplicative inverses.

Thus, log89×log98=1\log_8 9 \times \log_9 8 = 1, meaning 1log98=log89\frac{1}{\log_9 8} = \log_8 9.

Step 2: Substitute log89\log_8 9 with 1log98\frac{1}{\log_9 8} in the original fraction.

Given the expression is 2xlog89log98\frac{\frac{2x}{\log_8 9}}{\log_9 8}, it becomes:

2x1log98×1log98=2x×1=2x\frac{2x}{\frac{1}{\log_9 8}} \times \frac{1}{\log_9 8} = 2x \times 1 = 2x.

Step 3: Simplify the expression.

The multiplication results in the cancelling of the logarithmic terms through the multiplicative inverse relationship.

Therefore, the solution to the problem is 2x2x.

3

Final Answer

2x 2x

Key Points to Remember

Essential concepts to master this topic
  • Inverse Property: logba×logab=1 \log_b a \times \log_a b = 1 for all valid bases
  • Technique: Replace 1log98=log89 \frac{1}{\log_9 8} = \log_8 9 to simplify division
  • Check: Verify log89×log98=1 \log_8 9 \times \log_9 8 = 1 using calculator ✓

Common Mistakes

Avoid these frequent errors
  • Treating logarithms like regular fractions
    Don't add or subtract the bases and arguments like log89+log98=log1717 \log_8 9 + \log_9 8 = \log_{17} 17 = wrong answer! Logarithms follow special inverse properties, not fraction arithmetic. Always use the multiplicative inverse property: logba×logab=1 \log_b a \times \log_a b = 1 .

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 log89×log98=1 \log_8 9 \times \log_9 8 = 1 ?

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This is the change of base property in action! When you have logba \log_b a and logab \log_a b , they are multiplicative inverses because the bases and arguments are swapped.

How do I recognize when to use the inverse property?

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Look for two logarithms where the base of one equals the argument of the other. Like log89 \log_8 9 and log98 \log_9 8 - notice how 8 and 9 are swapped!

What happens to the 2x in this problem?

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The 2x 2x stays unchanged! When the logarithmic terms cancel out (because they equal 1), you're left with just 2x×1=2x 2x \times 1 = 2x .

Can I use a calculator to check this property?

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Absolutely! Calculate log89 \log_8 9 and log98 \log_9 8 separately, then multiply them. You should get very close to 1 (accounting for rounding errors).

Does this work with any bases?

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Yes! The property logba×logab=1 \log_b a \times \log_a b = 1 works for any positive bases (not equal to 1) and positive arguments. Try log25×log52=1 \log_2 5 \times \log_5 2 = 1 !

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