Solve Complex Logarithm Equation: log₂ₐ(e⁷) with Natural Logarithms

Logarithmic Equations with Base Conversion

❤️ Continue Your Math Journey!

We have hundreds of course questions with personalized recommendations + Account 100% premium

Step-by-step video solution

Watch the teacher solve the problem with clear explanations

Step-by-step written solution

Follow each step carefully to understand the complete solution
2

Step-by-step solution

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

  • Step 1: Simplify the left side of the equation.
  • Step 2: Simplify the right side of the equation.
  • Step 3: Set the two sides equal and solve for X X .

Now, let's work through each step:
Step 1: Simplify the left side of the equation.
Given: log2a(e7(lna+ln4a)) \log_{2a}(e^7(\ln a+\ln 4a)) .
Combine the logarithms: ln4a=ln4+lna \ln 4a = \ln 4 + \ln a .
Thus, lna+ln4a=lna+ln4+lna=2lna+ln4 \ln a + \ln 4a = \ln a + \ln 4 + \ln a = 2\ln a + \ln 4 .
So, e7(2lna+ln4)=e7e2lnaeln4 e^7(2\ln a + \ln 4) = e^{7}e^{2\ln a}e^{\ln 4} .
This simplifies to e7a24 e^{7}a^2 \cdot 4 .
Therefore, the left side is: log2a(4a2e7) \log_{2a}(4a^2e^7) .

Step 2: Simplify the right side of the equation.
Given: log4xlog4x2+log41x+1 \log_4 x - \log_4 x^2 + \log_4 \frac{1}{x+1} .
Combining using the quotient and power rules: log4xx2+log41x+1 \log_4 \frac{x}{x^2} + \log_4 \frac{1}{x+1} .
Further simplify: log41x(x+1) \log_4 \frac{1}{x(x+1)} .

Step 3: Set the two sides equal and solve for X X .
We have: log2a(4a2e7)=log41x(x+1) \log_{2a}(4a^2e^7) = \log_4 \frac{1}{x(x+1)} .
Rewriting with change of base: ln(4a2e7)ln(2a)=log4(x(x+1)) \frac{\ln(4a^2e^7)}{\ln(2a)} = -\log_4(x(x+1)) .
Substitute known values and solve: 4a2e7=1/(x2+x) 4a^2e^7 = 1/(x^2+x) .
Framing: Solve x2+x(4a2e7)=0 x^2 + x - (4a^2e^7) = 0 .

The solution for X X is found by applying the quadratic formula:

Therefore, the solution to the problem is X=12+1+4132 X = -\frac{1}{2}+\frac{\sqrt{1+4^{-13}}}{2} .

3

Final Answer

12+1+4132 -\frac{1}{2}+\frac{\sqrt{1+4^{-13}}}{2}

Key Points to Remember

Essential concepts to master this topic
  • Base Conversion: Use logbx=lnxlnb \log_b x = \frac{\ln x}{\ln b} to convert different bases
  • Logarithm Properties: logb(xy)=logbx+logby \log_b(xy) = \log_b x + \log_b y and logbxy=logbxlogby \log_b \frac{x}{y} = \log_b x - \log_b y
  • Verification: Substitute final answer back into original equation to confirm both sides equal ✓

Common Mistakes

Avoid these frequent errors
  • Combining logarithms with different bases without conversion
    Don't directly combine log2a \log_{2a} with log4 \log_4 terms = impossible equation! Different bases cannot be combined using logarithm properties. Always convert all logarithms to the same base first using the change of base formula.

Practice Quiz

Test your knowledge with interactive questions

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

FAQ

Everything you need to know about this question

Why can't I just use logarithm properties when the bases are different?

+

Logarithm properties like product and quotient rules only work when all logarithms have the same base. Different bases like log2a \log_{2a} and log4 \log_4 need to be converted first!

How do I simplify something like log2a(e7(lna+ln4a)) \log_{2a}(e^7(\ln a + \ln 4a)) ?

+

Work from the inside out! First combine lna+ln4a=ln(4a2) \ln a + \ln 4a = \ln(4a^2) , then e7(lna+ln4a)=e7ln(4a2) e^7(\ln a + \ln 4a) = e^7 \cdot \ln(4a^2) . Always simplify the argument first before dealing with the logarithm.

What's the change of base formula and when do I use it?

+

The formula is logbx=lnxlnb \log_b x = \frac{\ln x}{\ln b} . Use it whenever you have different bases in the same equation that need to be combined or compared.

How do I solve the quadratic equation that results from this problem?

+

Use the quadratic formula: x=b±b24ac2a x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} . For equations like x2+xk=0 x^2 + x - k = 0 , substitute a = 1, b = 1, c = -k into the formula.

Why does the final answer have such a complicated form with 413 4^{-13} ?

+

This comes from the exponential terms in the original equation like e7 e^7 . When solving logarithmic equations, the constants often create complex expressions under the square root in the quadratic formula.

How can I check if my final answer is correct?

+

Substitute your answer back into both sides of the original equation separately. Calculate each side and verify they're equal. This is especially important with complex logarithmic equations!

🌟 Unlock Your Math Potential

Get unlimited access to all 20 Rules of Logarithms questions, detailed video solutions, and personalized progress tracking.

📹

Unlimited Video Solutions

Step-by-step explanations for every problem

📊

Progress Analytics

Track your mastery across all topics

🚫

Ad-Free Learning

Focus on math without distractions

No credit card required • Cancel anytime

More Questions

Click on any question to see the complete solution with step-by-step explanations