Math Problem Statement

Solve the equation step by step ln(x+1)+ln(x)=ln(2)

Solution

We are tasked with solving the equation:

ln(x+1)+ln(x)=ln(2)\ln(x + 1) + \ln(x) = \ln(2)

Step 1: Use the logarithmic property

We can use the logarithmic property:

ln(a)+ln(b)=ln(ab)\ln(a) + \ln(b) = \ln(a \cdot b)

Thus, the left-hand side of the equation becomes:

ln((x+1)x)=ln(2)\ln((x + 1) \cdot x) = \ln(2)

This simplifies to:

ln(x(x+1))=ln(2)\ln(x(x + 1)) = \ln(2)

Step 2: Remove the natural logarithms

Since the natural logarithm functions on both sides of the equation are equal, the arguments must be equal. Therefore:

x(x+1)=2x(x + 1) = 2

Step 3: Expand the equation

Now, expand the left-hand side:

x2+x=2x^2 + x = 2

Step 4: Rearrange the equation into a quadratic form

Move all terms to one side to form a standard quadratic equation:

x2+x2=0x^2 + x - 2 = 0

Step 5: Solve the quadratic equation

We can solve this quadratic equation using factoring. We look for two numbers that multiply to 2-2 and add to 11. These numbers are 22 and 1-1, so we factor the quadratic as:

(x1)(x+2)=0(x - 1)(x + 2) = 0

Step 6: Find the solutions

Set each factor equal to zero:

x1=0orx+2=0x - 1 = 0 \quad \text{or} \quad x + 2 = 0

This gives us the solutions:

x=1orx=2x = 1 \quad \text{or} \quad x = -2

Step 7: Check for extraneous solutions

Since the logarithmic function is only defined for positive arguments, we must check the domain of the original equation. Both ln(x+1)\ln(x + 1) and ln(x)\ln(x) require x>0x > 0. Therefore, the solution x=2x = -2 is not valid.

Thus, the only valid solution is:

x=1x = 1

Would you like further clarification on any step?


Here are 5 related questions to deepen your understanding:

  1. How do we solve logarithmic equations with different bases?
  2. What is the domain of a logarithmic function?
  3. Can logarithmic equations have no solutions? If so, under what conditions?
  4. How can we solve a quadratic equation that cannot be factored easily?
  5. What are the key properties of logarithms that help in solving equations?

Tip: Always check the domain of logarithmic functions to ensure the solution is valid!

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Math Problem Analysis

Mathematical Concepts

Logarithmic Equations
Quadratic Equations
Logarithmic Properties

Formulas

ln(a) + ln(b) = ln(a * b)
Quadratic equation: ax^2 + bx + c = 0

Theorems

Logarithmic properties
Quadratic factoring

Suitable Grade Level

Grades 9-11