Solve Complex Logarithm Equation: Product of Log_a(x), Log_b(y), and Log_c(2)

Logarithmic Equations with Multiple Bases

logaxlogbylogc2=(logay3logay2)(logb12+logb22)logc(x2+1) \log_ax\log_by\log_c2=(\log_ay^3-\log_ay^2)(\log_b\frac{1}{2}+\log_b2^2)\log_c(x^2+1)

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:17 We'll use the logical subtraction formula, we'll get their logarithm
00:24 We'll use this formula in our exercise
00:35 We'll use the logical addition formula, we'll get the logarithm of their product
00:45 We'll use this formula in our exercise
01:10 Let's calculate and substitute
01:30 We'll use the logical multiplication formula, we'll switch between the numbers
01:45 We'll use this formula in our exercise
02:05 Let's reduce what we can
02:10 Again we'll use the logical multiplication formula
02:25 Let's reduce what we can
02:40 Let's compare the numbers and solve
02:45 Let's arrange the equation
02:55 We'll use the roots formula to find the possible solutions
03:09 There's no such thing as a negative root, therefore there's no solution to the question
03:19 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

logaxlogbylogc2=(logay3logay2)(logb12+logb22)logc(x2+1) \log_ax\log_by\log_c2=(\log_ay^3-\log_ay^2)(\log_b\frac{1}{2}+\log_b2^2)\log_c(x^2+1)

2

Step-by-step solution

To solve this problem, we must examine both sides of the equation:

The left-hand side of the equation:
logaxlogbylogc2 \log_a x \log_b y \log_c 2

The right-hand side of the equation:
(logay3logay2)(logb12+logb22)logc(x2+1) (\log_a y^3 - \log_a y^2)(\log_b \frac{1}{2} + \log_b 2^2)\log_c(x^2+1)

Let's simplify and understand both sides:

  • For logay3logay2 \log_a y^3 - \log_a y^2 , apply the power rule of logarithms:
    logay3=3logay \log_a y^3 = 3 \log_a y and logay2=2logay \log_a y^2 = 2 \log_a y
    Thus, logay3logay2=(3logay2logay)=logay \log_a y^3 - \log_a y^2 = (3 \log_a y - 2 \log_a y) = \log_a y .
  • For logb12+logb22 \log_b \frac{1}{2} + \log_b 2^2 , apply the rules:
    logb12=logb1logb2=logb2 \log_b \frac{1}{2} = \log_b 1 - \log_b 2 = -\log_b 2 and logb22=2logb2 \log_b 2^2 = 2 \log_b 2
    Thus, logb12+logb22=(logb2+2logb2)=logb2 \log_b \frac{1}{2} + \log_b 2^2 = (-\log_b 2 + 2 \log_b 2) = \log_b 2 .
  • Combine the simplifications for the right side:
    logaylogb2logc(x2+1) \log_a y \cdot \log_b 2 \cdot \log_c (x^2 + 1) .

Now the equation simplifies to:
logaxlogbylogc2=logaylogb2logc(x2+1) \log_a x \log_b y \log_c 2 = \log_a y \log_b 2 \log_c (x^2 + 1)

By inspection:

  • Both sides involve products of terms with different bases, which complicates direct comparison except where specific values are chosen.
  • Due to the nature of logarithms, for equalities of this form, the left-hand side and right-hand side must somehow equate if solutions exist.
  • Upon trying specific values became apparent as non-simple iterations seem to contradict basic logarithmic properties, ultimately showing complexities in natural number solutions.

Under these stringent conditions, it leads us to conclude:

Therefore, the solution to the given problem is No solution.

3

Final Answer

No solution

Key Points to Remember

Essential concepts to master this topic
  • Simplification: Use power rule and quotient rule to reduce complex expressions
  • Technique: Convert logay3logay2=(32)logay=logay \log_a y^3 - \log_a y^2 = (3-2)\log_a y = \log_a y
  • Check: Both sides must have compatible forms for solutions to exist ✓

Common Mistakes

Avoid these frequent errors
  • Ignoring logarithm domain restrictions and base compatibility
    Don't assume all logarithmic equations have solutions just because they can be simplified algebraically = impossible equations! This ignores that logarithms with different bases create incompatible relationships. Always check if the simplified forms can actually be equal given the domain constraints.

Practice Quiz

Test your knowledge with interactive questions

\( \frac{1}{\log_49}= \)

FAQ

Everything you need to know about this question

Why can't I just set the arguments equal when bases are different?

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You can only set arguments equal when the bases are the same! With different bases like logax \log_a x and logby \log_b y , you need to use change of base formula or other techniques.

How do I simplify expressions like log_a(y³) - log_a(y²)?

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Use the power rule: logay3=3logay \log_a y^3 = 3\log_a y and logay2=2logay \log_a y^2 = 2\log_a y . Then subtract: 3logay2logay=logay 3\log_a y - 2\log_a y = \log_a y .

What does it mean when a logarithmic equation has 'no solution'?

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It means there are no values that satisfy the equation within the allowed domain. This often happens when simplified forms create contradictions or when domain restrictions eliminate all possible solutions.

Can I multiply logarithms with different bases directly?

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No! Products like logaxlogby \log_a x \cdot \log_b y cannot be simplified using standard logarithm rules. You need to convert to the same base first or use special techniques.

How do I know if my simplification is correct?

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Check each step using logarithm properties: power rule, quotient rule, and product rule. For example, verify logb(1/2)+logb(22)=logb2+2logb2=logb2 \log_b(1/2) + \log_b(2^2) = -\log_b 2 + 2\log_b 2 = \log_b 2 .

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