Solve each logarithmic equation in Exercises 49–92. Be sure to reject any value of x that is not in the domain of the original logarithmic expressions. Give the exact answer. Then, where necessary, use a calculator to obtain a decimal approximation, correct to two decimal places, for the solution. log(x+4)=log x+log 4
Table of contents
- 0. Review of Algebra4h 18m
- 1. Equations & Inequalities3h 18m
- 2. Graphs of Equations1h 43m
- 3. Functions2h 17m
- 4. Polynomial Functions1h 44m
- 5. Rational Functions1h 23m
- 6. Exponential & Logarithmic Functions2h 28m
- 7. Systems of Equations & Matrices4h 5m
- 8. Conic Sections2h 23m
- 9. Sequences, Series, & Induction1h 22m
- 10. Combinatorics & Probability1h 45m
6. Exponential & Logarithmic Functions
Solving Exponential and Logarithmic Equations
Problem 79
Textbook Question
Solve each equation. Give solutions in exact form. ln ex - 2 ln e = ln e4
Verified step by step guidance1
Recall the properties of logarithms and exponents: \(\ln e^x = x\) and \(\ln e = 1\). Use these to simplify each term in the equation.
Rewrite the equation \(\ln e^x - 2 \ln e = \ln e^4\) as \(x - 2(1) = 4\) by applying the properties from step 1.
Simplify the left side to get \(x - 2 = 4\).
Solve the linear equation for \(x\) by adding 2 to both sides: \(x = 4 + 2\).
Express the solution in exact form as \(x = 6\).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Properties of Logarithms
Logarithmic properties such as the product, quotient, and power rules allow simplification of expressions. For example, ln(a^b) = b ln(a), and ln(x) - ln(y) = ln(x/y). These rules help rewrite and combine logarithmic terms to solve equations efficiently.
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Natural Logarithm and Exponential Functions
The natural logarithm (ln) is the inverse of the exponential function with base e. Understanding that ln(e^x) = x and e^(ln x) = x is crucial for solving equations involving ln and e, as it allows conversion between logarithmic and exponential forms.
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Solving Logarithmic Equations
Solving logarithmic equations involves isolating the logarithm, applying logarithmic properties, and then exponentiating both sides to eliminate the logarithm. This process yields exact solutions, often expressed in terms of constants like e or integers.
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