Math Problem Statement

log3(x−8)+log3(x−3)−log3x=1

Solution

We are given the equation:

log3(x8)+log3(x3)log3(x)=1\log_3(x - 8) + \log_3(x - 3) - \log_3(x) = 1

We can simplify this using the properties of logarithms.

Step 1: Combine the logarithmic terms

We can use the logarithmic property that states:

logb(A)+logb(B)=logb(AB)\log_b(A) + \log_b(B) = \log_b(A \cdot B)

Thus:

log3((x8)(x3))log3(x)=1\log_3((x - 8)(x - 3)) - \log_3(x) = 1

Next, we use the logarithmic subtraction property:

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

So, this becomes:

log3((x8)(x3)x)=1\log_3\left(\frac{(x - 8)(x - 3)}{x}\right) = 1

Step 2: Exponentiate both sides to eliminate the logarithm

Since log3(A)=1\log_3(A) = 1 implies A=31A = 3^1, we can rewrite the equation as:

(x8)(x3)x=3\frac{(x - 8)(x - 3)}{x} = 3

Step 3: Solve the equation

Multiply both sides by xx to eliminate the denominator:

(x8)(x3)=3x(x - 8)(x - 3) = 3x

Expand the left-hand side:

x23x8x+24=3xx^2 - 3x - 8x + 24 = 3x

Simplify:

x211x+24=3xx^2 - 11x + 24 = 3x

Move all terms to one side:

x214x+24=0x^2 - 14x + 24 = 0

Step 4: Solve the quadratic equation

Now we solve the quadratic equation x214x+24=0x^2 - 14x + 24 = 0. Using the quadratic formula:

x=(14)±(14)24(1)(24)2(1)x = \frac{-(-14) \pm \sqrt{(-14)^2 - 4(1)(24)}}{2(1)}

Simplify:

x=14±196962x = \frac{14 \pm \sqrt{196 - 96}}{2}

x=14±1002x = \frac{14 \pm \sqrt{100}}{2}

x=14±102x = \frac{14 \pm 10}{2}

So, we have two solutions:

x=14+102=242=12x = \frac{14 + 10}{2} = \frac{24}{2} = 12

x=14102=42=2x = \frac{14 - 10}{2} = \frac{4}{2} = 2

Step 5: Check for extraneous solutions

We need to check if these solutions make the arguments inside the logarithms positive. The arguments must satisfy x8>0x - 8 > 0, x3>0x - 3 > 0, and x>0x > 0.

For x=12x = 12:

  • 128=4>012 - 8 = 4 > 0
  • 123=9>012 - 3 = 9 > 0
  • 12>012 > 0

So, x=12x = 12 is a valid solution.

For x=2x = 2:

  • 28=62 - 8 = -6, which is negative.

Thus, x=2x = 2 is not a valid solution because it makes one of the logarithmic arguments negative.

Final Solution:

The only valid solution is x=12x = 12.


Would you like further details or have any questions?

Related Questions:

  1. How can logarithmic properties be applied to different bases?
  2. What are the steps to solve logarithmic inequalities?
  3. How do you graph logarithmic functions and their transformations?
  4. Can you explain how to solve logarithmic equations involving exponential terms?
  5. What are extraneous solutions, and how can you check for them?

Tip: Always check for extraneous solutions in logarithmic equations to ensure that the solution doesn't produce undefined expressions.

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Math Problem Analysis

Mathematical Concepts

Logarithms
Quadratic Equations
Logarithmic Properties

Formulas

log_b(A) + log_b(B) = log_b(A * B)
log_b(A) - log_b(B) = log_b(A / B)
Quadratic Formula: x = (-b ± √(b² - 4ac)) / 2a

Theorems

Properties of Logarithms
Quadratic Formula

Suitable Grade Level

Grades 9-12