Math Problem Statement

Algebraically solve log(6x + 4) = 5 + log(2x − 5) for x. (Enter your answers as a comma-separated list. If there is no solution, enter NO SOLUTION.)

Solution

To solve the equation log(6x+4)=5+log(2x5)\log(6x + 4) = 5 + \log(2x - 5) for xx, we can proceed as follows:

  1. Rewrite the equation: Move all logarithmic terms to one side of the equation: log(6x+4)log(2x5)=5\log(6x + 4) - \log(2x - 5) = 5

  2. Apply the properties of logarithms: Use the quotient rule for logarithms, log(a)log(b)=log(ab)\log(a) - \log(b) = \log\left(\frac{a}{b}\right), to combine the logs: log(6x+42x5)=5\log\left(\frac{6x + 4}{2x - 5}\right) = 5

  3. Rewrite in exponential form: To remove the logarithm, rewrite the equation in exponential form. Since the base of a common logarithm is 10, we get: 6x+42x5=105\frac{6x + 4}{2x - 5} = 10^5 Simplify 10510^5 as 100000100000: 6x+42x5=100000\frac{6x + 4}{2x - 5} = 100000

  4. Cross-multiply to clear the fraction: 6x+4=100000(2x5)6x + 4 = 100000 \cdot (2x - 5) Expanding on the right: 6x+4=200000x5000006x + 4 = 200000x - 500000

  5. Isolate xx: Move all terms involving xx to one side of the equation and constant terms to the other: 4+500000=200000x6x4 + 500000 = 200000x - 6x Simplify: 500004=199994x500004 = 199994x

  6. Solve for xx: x=500004199994=2.50005x = \frac{500004}{199994} = 2.50005

  7. Check for extraneous solutions: Substitute x=2.50005x = 2.50005 back into the original expressions inside the logarithms to ensure they are positive:

    • 6x+4=6(2.50005)+4=15.0003+4=19.00036x + 4 = 6(2.50005) + 4 = 15.0003 + 4 = 19.0003, which is positive.
    • 2x5=2(2.50005)5=5.00015=0.00012x - 5 = 2(2.50005) - 5 = 5.0001 - 5 = 0.0001, which is also positive.

Since both expressions inside the logarithms are positive, x=2.50005x = 2.50005 is valid.

Final Answer:

x=2.50005x = 2.50005

Would you like further explanation on any step, or have questions about this problem?

Here are five related questions for further exploration:

  1. How can you apply logarithmic properties in equations involving different bases?
  2. What are extraneous solutions, and why are they important in logarithmic equations?
  3. How would this problem differ if a different base were used?
  4. Why do we need to ensure that terms inside logarithms remain positive?
  5. What is the process of converting between logarithmic and exponential forms?

Tip: Always check your solution back in the original equation to avoid extraneous solutions, especially with logarithmic functions where domains are restricted to positive values.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Algebra
Logarithmic Equations
Exponential Equations

Formulas

log(a) - log(b) = log(a/b)
log(x) = y → x = 10^y

Theorems

Properties of logarithms
Quotient rule for logarithms

Suitable Grade Level

Grades 9-12