Math Problem Statement

Solve the following logarithmic equation:log7x + log7(3x-2) = 0

Solution

We are given the equation:

log7x+log7(3x2)=0\log_7{x} + \log_7{(3x - 2)} = 0

Step 1: Apply the Logarithmic Property

We can use the logarithmic property:

logbA+logbB=logb(AB)\log_b{A} + \log_b{B} = \log_b{(A \cdot B)}

Thus, the equation becomes:

log7(x(3x2))=0\log_7{(x \cdot (3x - 2))} = 0

Step 2: Simplify the Equation

Now simplify the expression inside the logarithm:

log7(x(3x2))=0\log_7{(x(3x - 2))} = 0

This simplifies further to:

log7(3x22x)=0\log_7{(3x^2 - 2x)} = 0

Step 3: Eliminate the Logarithm

Since log7A=0\log_7{A} = 0 implies A=1A = 1, we can write:

3x22x=13x^2 - 2x = 1

Step 4: Rearrange the Equation

Rearrange the equation to form a quadratic:

3x22x1=03x^2 - 2x - 1 = 0

Step 5: Solve the Quadratic Equation

Now, solve the quadratic equation using the quadratic formula:

x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

For 3x22x1=03x^2 - 2x - 1 = 0, the coefficients are a=3a = 3, b=2b = -2, and c=1c = -1. Substituting these into the quadratic formula:

x=(2)±(2)24(3)(1)2(3)x = \frac{-(-2) \pm \sqrt{(-2)^2 - 4(3)(-1)}}{2(3)}

x=2±4+126x = \frac{2 \pm \sqrt{4 + 12}}{6}

x=2±166x = \frac{2 \pm \sqrt{16}}{6}

x=2±46x = \frac{2 \pm 4}{6}

Step 6: Calculate the Solutions

Now solve for the two possible values of xx:

x=2+46=66=1x = \frac{2 + 4}{6} = \frac{6}{6} = 1

x=246=26=13x = \frac{2 - 4}{6} = \frac{-2}{6} = -\frac{1}{3}

Step 7: Check for Valid Solutions

Since logarithms are only defined for positive values of their arguments, we need to check which solutions are valid:

  • For x=1x = 1, both log7(1)\log_7(1) and log7(3(1)2)\log_7(3(1) - 2) are valid.
  • For x=13x = -\frac{1}{3}, the logarithmic terms become undefined (since xx must be positive).

Thus, the only valid solution is:

x=1x = 1

Final Answer:

x=1x = 1

Would you like more details on any of these steps, or have any further questions?

5 Related Questions:

  1. How do you solve logarithmic equations with different bases?
  2. Can you solve log2x+log2(x1)=3\log_2{x} + \log_2{(x - 1)} = 3?
  3. What are the properties of logarithms used in solving equations?
  4. How can you graph logarithmic functions and their transformations?
  5. How do you solve logarithmic inequalities?

Tip:

Always check the domain of the logarithmic equation to ensure solutions make the argument of the logarithms positive.

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Math Problem Analysis

Mathematical Concepts

Logarithmic Equations
Algebra
Quadratic Equations

Formulas

log_b{A} + log_b{B} = log_b{(A * B)}
Quadratic formula: x = (-b ± √(b^2 - 4ac)) / 2a

Theorems

Logarithmic properties
Quadratic formula

Suitable Grade Level

Grades 10-12