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For individual or group investigation (Exercises \(97-102\) ) Work Exercises \(97-102\) in order. Solve \(0=-3^{x}+7\) for \(x,\) expressing \(x\) in terms of base 3 logarithm.

Short Answer

Expert verified
\(x = \log_3(7)\)

Step by step solution

01

Isolate the Exponential Term

Start by isolating the term with the exponent. The equation is \(0 = -3^x + 7\). Add \(3^x\) to both sides to get \(3^x = 7\).
02

Apply Logarithms

To express \(x\) in terms of the logarithm of base 3, take the logarithm on both sides. Using \(\log_3\), we have: \[ \log_3(3^x) = \log_3(7) \]
03

Use the Power Rule of Logarithms

Apply the power rule of logarithms, which states \(\log_b(a^n) = n \cdot \log_b(a)\), on the left side: \[ x \cdot \log_3(3) = \log_3(7) \]
04

Simplify the Logarithms

Knowing that \(\log_3(3) = 1\), simplify the equation: \[ x \cdot 1 = \log_3(7) \] Thus, we have \(x = \log_3(7)\).

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Key Concepts

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

Logarithms
A logarithm is essentially a tool used to determine how many times a number, known as the base, must be multiplied by itself to produce another number. For example, if we have \( log_b(a) \), it tells us what power \( b \) needs to be raised to in order to get \( a \). Logarithms are incredibly useful in solving exponential equations because they allow us to work backwards from an exponential form.In the context of the given problem, logarithms help us express the variable \( x \) from an exponential equation. Specifically, we are using logarithms of base 3 to resolve the component of the equation where 3 is the base and we need to determine the exponent \( x \). By understanding how logarithms work, you can convert from an exponential equation format into a more workable numeric expression.
Power Rule of Logarithms
The power rule of logarithms is a very handy property that simplifies exponentials within logarithmic expressions. It states that \( \log_b(a^n) = n \cdot \log_b(a) \), meaning that the exponent \( n \) can be pulled out and multiplied by the logarithm itself. This is useful because it allows us to deal with exponents outside of the logarithmic operation, making complex expressions much simpler.In our exercise, after taking the logarithm of both sides, we use the power rule to simplify \( \log_3(3^x) \). This expression becomes \( x \cdot \log_3(3) \). Since \( \log_3(3) = 1 \) (as any number log base of itself is 1), the expression simplifies further to just \( x \). This step is crucial for isolating the variable \( x \), allowing us to solve the equation easily.
Base 3 Logarithm
A base 3 logarithm is simply a logarithm where the base is 3. It is written as \( \log_3 \), and it helps us find out how many times 3 must be multiplied by itself to achieve a certain number. In other words, if you have \( \log_3(a) \), it represents the power that 3 needs to be raised to in order to equal \( a \).In solving the original exercise, converting \( 3^x = 7 \) to \( \log_3(7) \) is a pivotal step. This converts the exponential equation into a logarithmic one, allowing us to clearly see that \( x \) is simply \( \log_3(7) \). Understanding how to switch between these representations is an essential skill in mastering problems involving exponential equations.
Solving Equations
Solving equations, especially exponential ones, often involves isolating the variable in question. This can require a combination of arithmetic operations and the application of mathematical properties like logarithms. In our original exercise, the goal was to solve for \( x \) in the equation \( 0 = -3^x + 7 \).Here are simple steps:
  • Isolate the exponential term: By manipulating the equation, bring the term \( 3^x \) to one side, resulting in \( 3^x = 7 \).
  • Apply logarithms: Take the logarithm of both sides to manage the exponential, specifically using \( \log_3 \).
  • Simplify using the power rule: Use the property \( \log_b(a^n) = n \cdot \log_b(a) \) to extract the exponent \( x \).
  • Solve for the variable: After simplifying, you'll have \( x = \log_3(7) \), solving the equation clearly and efficiently.
Each of these steps plays a crucial role in converting a complex problem into a straightforward solution, illustrating the power of understanding and applying logarithms.

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Most popular questions from this chapter

Newton's law of cooling says that the rate at which an object cools is proportional to the difference \(C\) in temperature between the object and the environment around it. The temperature \(f(t)\) of the object at time t in appropriate units after being introduced into an environment with a constant temperature \(T_{0}\) is $$f(t)=T_{0}+C e^{-k t}$$ where \(C\) and \(k\) are constants. Use this result. A piece of metal is heated to \(300^{\circ} \mathrm{C}\) and then placed in a cooling liquid at \(50^{\circ} \mathrm{C}\). After 4 minutes, the metal has cooled to \(175^{\circ} \mathrm{C}\). Estimate its temperature after 12 minutes.

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