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 2=log(5x+1)
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 87
Textbook Question
Solve each equation for the indicated variable. Use logarithms with the appropriate bases. p = a + (k/ln x), for x
Verified step by step guidance1
Start with the given equation: \(p = a + \frac{k}{\ln x}\).
Isolate the term containing \(x\) by subtracting \(a\) from both sides: \(p - a = \frac{k}{\ln x}\).
Next, solve for \(\ln x\) by taking the reciprocal and multiplying both sides by \(k\): \(\ln x = \frac{k}{p - a}\).
Recall that \(\ln x\) means the natural logarithm of \(x\), so to solve for \(x\), rewrite the equation in exponential form: \(x = e^{\frac{k}{p - a}}\).
This expression gives \(x\) in terms of \(p\), \(a\), and \(k\), using the natural exponential function.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Solving Equations for a Specific Variable
This involves isolating the variable of interest on one side of the equation. It requires algebraic manipulation such as addition, subtraction, multiplication, division, and applying inverse operations to rewrite the equation in terms of the desired variable.
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Equations with Two Variables
Properties of Logarithms
Logarithms are the inverses of exponential functions and have specific properties like the product, quotient, and power rules. Understanding these properties helps simplify expressions and solve equations involving logarithms with different bases.
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Natural Logarithm and the Constant e
The natural logarithm (ln) is the logarithm with base e, where e ≈ 2.718. It is commonly used in calculus and algebra to solve equations involving growth, decay, or continuous compounding. Recognizing when to apply ln and how to manipulate it is essential for solving equations like p = a + (k/ln x).
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