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Solve for \(x\) by changing to exponential form. Round your answer to three decimal places. a. \(\ln 3 x=1\) b. \(3 \ln x=5\) c. \(\ln 3+\ln x=1.5\)

Short Answer

Expert verified
a. \(x \approx 0.906\), b. \(x \approx 5.294\), c. \(x \approx 1.494\).

Step by step solution

01

Solve for part (a) \(\ln 3x = 1\)

To solve for x, we first need to change the logarithmic form to exponential form. The logarithmic form \(\ln 3x = 1\) can be written as \(\text{e}^1 = 3x\).
02

Isolate x in part (a)

Divide both sides by 3 to isolate x: \(\frac{\text{e}^1}{3} = x\). This simplifies to \(x = \frac{\text{e}}{3}\).
03

Calculate the value of x for part (a)

Compute the value using a calculator: \(x = \frac{2.718}{3} \approx 0.906\). Round the answer to three decimal places: \(x \approx 0.906\).
04

Solve for part (b) \ (3 \ln x = 5)\

Divide both sides by 3 to isolate \(\ln x\): \(\ln x = \frac{5}{3}\).
05

Change to exponential form for part (b)

Rewrite the equation in exponential form: \(\text{e}^{\frac{5}{3}} = x\).
06

Calculate the value of x for part (b)

Compute the value using a calculator: \(x \approx \text{e}^{1.667} \approx 5.294\). Round the answer to three decimal places: \(x \approx 5.294\).
07

Solve for part (c) \(\ln 3 + \ln x = 1.5\)

Combine the logarithms using the product property: \(\text{ln}(3x) = 1.5\).
08

Change to exponential form for part (c)

Rewrite the equation in exponential form: \(3x = \text{e}^{1.5}\).
09

Isolate x in part (c)

Divide both sides by 3 to isolate x: \(x = \frac{\text{e}^{1.5}}{3}\).
10

Calculate the value of x for part (c)

Use a calculator to find \(x = \frac{4.481}{3} \approx 1.494\). Round the answer to three decimal places: \(x \approx 1.494\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

logarithmic form
Logarithmic equations help us solve for variables hidden within a logarithm. The general form of a logarithmic equation is given by \(\text{log}_b(y) = x\), where \(b\) is the base of the logarithm, \(y\) is the argument, and \(x\) is the exponent or the result. Understanding how to manipulate these forms is essential in solving logarithmic equations. For example, in part (a) \(\text{ln }3x = 1\), \(\ln\) represents the natural logarithm, which has a base \(e\). We need to transition from this form to its exponential counterpart to solve for \(x\).
exponential form
Converting from logarithmic to exponential form makes solving easier. If you have \(\text{log}_b(y) = x\), it can be rewritten in exponential form as \(b^x = y\). Let's see an example: For the equation \(\ln 3x = 1\), the natural logarithm with base \(e\) converts directly to \(e^1 = 3x\). This is a critical step, as it allows us to work with exponentiation rather than logarithms, making it easier to isolate the variable.
isolating variables
Isolating variables is a fundamental algebraic skill, necessary for solving equations irrespective of their form—linear, logarithmic, or exponential. In the case of \(e^1 = 3x\) from part (a), we isolate \(x\) by dividing both sides by 3, giving \(\frac{e^1}{3} = x\). Similarly, for part (b) \(3 \ln x = 5\), we divide both sides by 3 to solve for \(\ln x\): \(\ln x = \frac{5}{3}\). This step simplifies our work and directly leads to the solution.
rational exponents
Rational exponents reflect fractional powers and can frequently appear when dealing with exponential equations. For instance, when converting back to the exponential form, like \(\ln x = \frac{5}{3}\) becoming \(e^\frac{5}{3} = x\), we see a rational exponent in action. Using a calculator to compute \(e^\frac{5}{3}\), we can readily find \(\text{e}^{1.667} \approx 5.294\). Rational exponents are crucial in rendering complex exponential equations accessible and more straightforward to solve.

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Most popular questions from this chapter

Determine which data sets (if any) describe \(y\) as an exponential function of \(x\), then construct the exponential function. a. $$ \begin{aligned} &\text { a. }\\\ &\begin{array}{cc} \hline x & \log y(\text { or } Y) \\ \hline 0 & 2.30103 \\ 10 & 4.30103 \\ 20 & 4.90309 \\ 30 & 5.25527 \\ 40 & 5.50515 \\ \hline \end{array} \end{aligned} $$ b. $$ \begin{array}{rr} \hline x & \log y \text { (or } Y \text { ) } \\ \hline 0 & 4.77815 \\ 10 & 3.52876 \\ 20 & 2.27938 \\ 30 & 1.02999 \\ 40 & -0.21945 \\ \hline \end{array} $$

Prove Rule 3 of common logarithms: \(\log A^{p}=p \log A\) (where \(A>0)\)

(Requires a graphing program.) Using technology, graph the functions \(f(x)=15,000 e^{0.085 x}\) and \(g(x)=100,000\) on the same grid. a. Estimate the point of intersection. (Hint: Let \(x\) go from 0 to \(60 .)\) b. If \(f(x)\) represents the amount of money accumulated by investing at a continuously compounded rate (where \(x\) is in years), explain what the point of intersection represents.

Expand each logarithm using only the numbers \(2,5, \ln 2,\) and \(\ln 5 .\) a. \(\ln 25\) b. \(\ln 250\) c. \(\ln 625\)

Wikipedia is a popular, free online encyclopedia (at \(e n .\) wikipedia.org) that anyone can edit. (So articles should be taken with "a grain of salt.") One Wikipedia article claims that the number of articles posted on Wikipedia has been growing exponentially since October 23,2002 . At that date there were approximately 90 thousand articles posted, and the growth rate was about \(0.2 \%\) per day. a. Create an exponential model for the growth in Wikipedia articles. b. What is the doubling time? Interpret your answer.

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