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+log(x+3)=log 10
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 91
Textbook Question
Solve each equation for the indicated variable. Use logarithms with the appropriate bases.
Verified step by step guidance1
Identify the given equation: \(I = \frac{E}{R} \left(1 - e^{-\frac{Rt}{2}}\right)\), and the goal is to solve for the variable \(t\).
Isolate the exponential term by first multiplying both sides by \(R\) to get rid of the denominator: \(IR = E \left(1 - e^{-\frac{Rt}{2}}\right)\).
Divide both sides by \(E\) to isolate the expression with the exponential: \(\frac{IR}{E} = 1 - e^{-\frac{Rt}{2}}\).
Rearrange to isolate the exponential term: \(e^{-\frac{Rt}{2}} = 1 - \frac{IR}{E}\).
Take the natural logarithm (ln) of both sides to solve for \(t\): \(-\frac{Rt}{2} = \ln\left(1 - \frac{IR}{E}\right)\), then multiply both sides by \(-\frac{2}{R}\) to isolate \(t\).
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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 addition, subtraction, multiplication, division, and applying inverse operations to both sides to express the variable explicitly.
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Equations with Two Variables
Exponential Functions and Their Properties
Exponential functions have variables in the exponent, like e^x. Understanding their behavior and how to manipulate them is essential, especially recognizing that the natural exponential function e^x is the inverse of the natural logarithm.
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Logarithms and Their Use in Solving Exponential Equations
Logarithms are the inverse operations of exponentials and are used to solve equations where the variable is in the exponent. Applying logarithms with the appropriate base allows you to 'bring down' the exponent and solve for the variable.
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