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

Question

Given 0<a , find X:

log2ae7(lna+ln4a)=log4xlog4x2+log41x+1 \log_{2a}e^7(\ln a+\ln4a)=\log_4x-\log_4x^2+\log_4\frac{1}{x+1}

Video Solution

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} .

Answer

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


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