Solve the Logarithm Expression: 2log₈2 + log₈3

Logarithm Properties with Power and Product Rules

2log82+log83= 2\log_82+\log_83=

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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 use the power log formula
00:15 Let's use this formula in our exercise
00:21 Let's solve the power
00:33 Let's use the logarithm addition formula
00:39 Let's use this formula in our exercise
00:50 Let's solve the parentheses
00:55 And this is the solution to the question

Step-by-step written solution

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1

Understand the problem

2log82+log83= 2\log_82+\log_83=

2

Step-by-step solution

2log82=log822=log84 2\log_82=\log_82^2=\log_84

2log82+log83=log84+log83= 2\log_82+\log_83=\log_84+\log_83=

log843=log812 \log_84\cdot3=\log_812

3

Final Answer

log812 \log_812

Key Points to Remember

Essential concepts to master this topic
  • Power Rule: 2log82=log822=log84 2\log_82 = \log_82^2 = \log_84
  • Product Rule: log84+log83=log8(43)=log812 \log_84 + \log_83 = \log_8(4 \cdot 3) = \log_812
  • Check: Verify that 8log812=12 8^{\log_812} = 12 and 22+3=712 2 \cdot 2 + 3 = 7 \neq 12

Common Mistakes

Avoid these frequent errors
  • Adding logarithms instead of multiplying their arguments
    Don't think log84+log83=log8(4+3)=log87 \log_84 + \log_83 = \log_8(4+3) = \log_87 ! This confuses addition of logarithms with addition of their arguments, giving the wrong answer. Always remember that logax+logay=loga(xy) \log_a x + \log_a y = \log_a(xy) - you multiply the arguments, not add them.

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 2log82 2\log_82 become log84 \log_84 ?

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This uses the power rule for logarithms: nlogax=logaxn n\log_a x = \log_a x^n . So 2log82=log822=log84 2\log_82 = \log_8 2^2 = \log_8 4 . The coefficient becomes an exponent!

How do I know when to add logarithms vs multiply their arguments?

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Key rule: When you add logarithms with the same base, you multiply their arguments: logax+logay=loga(xy) \log_a x + \log_a y = \log_a(xy) . Don't add the arguments - that's the most common mistake!

What if the logarithms had different bases?

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You cannot directly combine logarithms with different bases using these rules. You'd need to convert them to the same base first using the change of base formula: logbx=logaxlogab \log_b x = \frac{\log_a x}{\log_a b} .

How can I check if log812 \log_812 is correct?

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Ask yourself: "What power of 8 gives me 12?" Since 81=8 8^1 = 8 and 82=64 8^2 = 64 , the answer should be between 1 and 2. Also verify: 223=43=12 2^2 \cdot 3 = 4 \cdot 3 = 12

Why can't I just calculate 22+3=7 2 \cdot 2 + 3 = 7 ?

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That would be treating the logarithm expression like regular arithmetic! Remember, log82 \log_82 is asking "what power of 8 gives 2?" - it's not equal to 2 itself. Always apply logarithm properties first.

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