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. 2 log x−log 7=log 112
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 88
Textbook Question
Solve each equation for the indicated variable. Use logarithms with the appropriate bases. r = p - k ln t, for t
Verified step by step guidance1
Start with the given equation: \(r = p - k \ln t\).
Isolate the logarithmic term by subtracting \(p\) from both sides: \(r - p = -k \ln t\).
Divide both sides by \(-k\) to solve for \(\ln t\): \(\frac{r - p}{-k} = \ln t\).
Rewrite the equation in exponential form to solve for \(t\): \(t = e^{\frac{r - p}{-k}}\).
Simplify the exponent if desired, noting that dividing by \(-k\) is the same as multiplying by \(-\frac{1}{k}\).
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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 indicated variable on one side of the equation. It requires algebraic manipulation such as adding, subtracting, multiplying, dividing, and applying inverse operations to both sides to express the variable explicitly.
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Equations with Two Variables
Properties of Logarithms
Logarithms are the inverses of exponential functions. Key properties include the product, quotient, and power rules, which help simplify expressions and solve equations involving logarithms. Understanding these properties is essential for manipulating terms like ln t.
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Natural Logarithm (ln) and Its Inverse
The natural logarithm, denoted ln, is the logarithm with base e. To solve for a variable inside a natural log, you often exponentiate both sides using e as the base, effectively applying the inverse operation to isolate the variable.
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