Solve the Logarithmic Equation: ln x + ln(x+1) - ln2 = 3

Solve for X:

lnx+ln(x+1)ln2=3 \ln x+\ln(x+1)-\ln2=3

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:04 We'll use the formula for combining non-i's, we'll get where they multiplied
00:19 We'll use this formula in our exercise
00:29 We'll use the formula for subtracting non-i's, we'll get where they divided
00:35 We'll use this formula in our exercise
00:55 We'll use the definition of where, and solve
01:10 We'll multiply by 2 to eliminate the fraction
01:20 We'll open parentheses properly, multiply by each factor
01:30 We'll arrange the equation
01:55 We'll use the root formula to find possible solutions
02:10 We'll calculate and solve
02:35 We'll always remember there are 2 possibilities, addition and subtraction
02:56 We'll find the domain of definition
03:11 This is the domain of definition, with it we'll find the solution
03:21 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

Solve for X:

lnx+ln(x+1)ln2=3 \ln x+\ln(x+1)-\ln2=3

2

Step-by-step solution

The equation to solve is lnx+ln(x+1)ln2=3 \ln x + \ln(x+1) - \ln 2 = 3 .

Step 1: Combine the logarithms using the product and quotient rules:

ln(x(x+1))ln2=3becomesln(x(x+1)2)=3. \ln (x(x+1)) - \ln 2 = 3 \quad \text{becomes} \quad \ln \left(\frac{x(x+1)}{2}\right) = 3.

Step 2: Eliminate the logarithm by exponentiating both sides:

x(x+1)2=e3. \frac{x(x+1)}{2} = e^3.

Step 3: Solve for x x by clearing the fraction:

x(x+1)=2e3. x(x+1) = 2e^3.

Step 4: Expand and set up a quadratic equation:

x2+x2e3=0. x^2 + x - 2e^3 = 0.

Step 5: Use the quadratic formula x=b±b24ac2a x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} , where a=1 a = 1 , b=1 b = 1 , and c=2e3 c = -2e^3 :

x=1±124×1×(2e3)2×1. x = \frac{-1 \pm \sqrt{1^2 - 4 \times 1 \times (-2e^3)}}{2 \times 1}.

Step 6: Simplify under the square root:

x=1±1+8e32. x = \frac{-1 \pm \sqrt{1 + 8e^3}}{2}.

Step 7: Ensure x>0 x > 0 . Given 1+8e3 \sqrt{1 + 8e^3} will be positive, 1+1+8e32 \frac{-1 + \sqrt{1 + 8e^3}}{2} is the valid solution.

Therefore, the solution to the problem is 1+1+8e32 \frac{-1+\sqrt{1+8e^3}}{2} .

3

Final Answer

1+1+8e32 \frac{-1+\sqrt{1+8e^3}}{2}

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

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