Math Problem Statement

Solve the following equation.

log7(x + 5) − log7(x − 1) = 1

Solution

We are given the logarithmic equation:

log7(x+5)log7(x1)=1\log_7(x + 5) - \log_7(x - 1) = 1

Step 1: Use the logarithm subtraction rule.

The logarithm subtraction rule states that:

logb(A)logb(B)=logb(AB)\log_b(A) - \log_b(B) = \log_b\left(\frac{A}{B}\right)

Apply this to the given equation:

log7(x+5x1)=1\log_7\left(\frac{x + 5}{x - 1}\right) = 1

Step 2: Rewrite the equation in exponential form.

Since logb(A)=C\log_b(A) = C implies A=bCA = b^C, we can rewrite the equation as:

x+5x1=71\frac{x + 5}{x - 1} = 7^1

Simplifying:

x+5x1=7\frac{x + 5}{x - 1} = 7

Step 3: Solve for xx.

Multiply both sides by x1x - 1 to clear the fraction:

x+5=7(x1)x + 5 = 7(x - 1)

Expand and solve for xx:

x+5=7x7x + 5 = 7x - 7

Subtract xx from both sides:

5=6x75 = 6x - 7

Add 7 to both sides:

12=6x12 = 6x

Divide by 6:

x=2x = 2

Step 4: Verify the solution.

Substitute x=2x = 2 back into the original logarithmic expressions to ensure they are valid:

log7(2+5)log7(21)=log7(7)log7(1)\log_7(2 + 5) - \log_7(2 - 1) = \log_7(7) - \log_7(1)

This simplifies to:

log7(7)log7(1)=10=1\log_7(7) - \log_7(1) = 1 - 0 = 1

The solution is valid.

Final Answer:

The solution to the equation log7(x+5)log7(x1)=1\log_7(x + 5) - \log_7(x - 1) = 1 is:

x=2x = 2

Would you like more details or have any questions? Here are some related problems to practice:

  1. Solve log2(x+3)log2(x1)=2\log_2(x + 3) - \log_2(x - 1) = 2.
  2. Solve log5(3x+1)=2\log_5(3x + 1) = 2.
  3. Solve log10(x+4)=2+log10(x)\log_{10}(x + 4) = 2 + \log_{10}(x).
  4. Solve log4(x24)=1\log_4(x^2 - 4) = 1.
  5. Solve 2log3(x)=log3(9)2\log_3(x) = \log_3(9).

Tip: Always check the domain of the logarithmic expressions to ensure the argument inside the logarithm is positive.

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Math Problem Analysis

Mathematical Concepts

Logarithms
Equations

Formulas

Logarithm subtraction rule

Theorems

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Suitable Grade Level

Grades 10-12