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Solve the system. $$ \begin{array}{r} \log x+2 \log y=5 \\ 2 \log x-\log y=0 \end{array} $$

Short Answer

Expert verified
The solution to the system is \( x = 10 \) and \( y = 100 \).

Step by step solution

01

Use properties of logarithms

Recall the properties of logarithms: 1. \textbf{Product rule}: \(\log_b(xy) = \log_b(x) + \log_b(y)\) 2. \textbf{Power rule}: \(\log_b(x^n) = n \log_b(x)\)
02

Apply properties to the first equation

Given first equation: \ \( \log x + 2 \log y = 5 \). Using the \text{power rule} for logarithms, this becomes: \( \log x + \log y^2 = 5 \) Using the \text{product rule} for logarithms: \( \log(x y^2) = 5 \). Rewrite in exponential form: \( x y^2 = 10^5 \).
03

Apply properties to the second equation

Given second equation: \ \( 2 \log x - \log y = 0 \). Using the \text{product rule} for logarithms: \( \log(x^2) - \log(y) = 0 \) Using the \text{quotient rule} for logarithms: \( \log \left(\frac{x^2}{y} \right) = 0 \). Rewrite in exponential form: \( \frac{x^2}{y} = 10^0 \). Simplify: \( \frac{x^2}{y} = 1 \), So \( x^2 = y \).
04

Substitute y in the equation

Using the second equation, substitute \( y = x^2 \) into the first equation: \( x (x^2)^2 = 10^5 \) Which simplifies to \ \( x^5 = 10^5 \)
05

Solve for x

Solving \( x^5 = 10^5 \) by taking the fifth root of both sides: \ \( x = 10 \)
06

Solve for y

Substituting \( x = 10 \) back into \ y = x^2 \, obtain: \( y = 10^2 = 100 \)

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Key Concepts

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

Logarithmic Properties
In logarithms, understanding the fundamental properties is pivotal for solving equations. These properties are:
  • Product rule: If you have \(\log_b(xy) = \log_b(x) + \log_b(y)\)
  • Quotient rule: For division, \(\log_b\left(\frac{x}{y}\right) = \log_b(x) - \log_b(y)\)
  • Power rule: Raising a number to a power inside the log results in \(\log_b(x^n) = n \log_b(x)\)
These properties are used to manipulate the terms in logarithmic equations. By applying these rules, complex logarithmic expressions can be simplified and even transformed into exponential equations. This is essential for solving the logarithmic systems. Remember to always look out for potential properties to apply in order to simplify your logarithmic equations.
Exponential Form
Transforming a logarithmic equation into its exponential form is a technique that simplifies solving for variables. For any logarithmic equation \(\log_b(x) = y\), its equivalent exponential form is \(b^y = x\).

For example, consider \(\log(xy^2) = 5\). You can rewrite this using the exponential form \(xy^2 = 10^5\). This transformation turns difficult logarithmic equations into more manageable polynomial equations. Using exponential form allows us to solve for variables without needing to directly handle the logarithmic expressions, which often simplifies the problem significantly.
Substitution Method
The substitution method is a powerful algebraic tool for solving systems of equations. Here's how it works:

1. Solve one of the equations for one variable in terms of the other variables.
2. Substitute this expression into the second equation.
3. Solve the resulting equation for the remaining variable.

In the given problem, we solved the second equation, \(2 \log x - \log y = 0\) to find that \(y = x^2\). By substituting \(y = x^2\) into the first equation, we transformed the system into a single equation involving only one variable, \(x\). This makes it much easier to solve. Finally, substitute back in to find \(y\). The substitution method helps break complex systems into simpler, more manageable steps.
Algebraic Manipulation
Algebraic manipulation involves the rearrangement of equations using basic algebraic operations: addition, subtraction, multiplication, and division. This process is crucial when transforming and simplifying equations.

1. **Simplify** the terms: Use the properties of logarithms to combine or break down expressions.
2. **Isolate** variables: Move terms involving the variable you're solving for to one side of the equation and constants to the other.
3. **Solve** the simplified equation: This often involves further simplification or applying specific techniques like taking roots or powers.

In the solved problem, we transformed logarithmic forms into exponential forms and then simplified the resulting algebraic equations. The steps involved taking roots and substituting back to isolate and solve for the terms directly. The power of algebraic manipulation lies in its ability to make complex equations more straightforward to handle.

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Most popular questions from this chapter

A large department store needs at least 3600 labor hours covered per week. It employs full-time staff \(40 \mathrm{hr} / \mathrm{wk}\) and part-time staff \(25 \mathrm{hr} / \mathrm{wk}\). The cost to employ a full-time staff member is more because the company pays benefits such as health care and life insurance. $$ \begin{array}{|l|c|c|} \hline & \text { Hours per Week } & \text { Cost per Hour } \\ \hline \text { Full time } & 40 \mathrm{hr} & \$ 20 \\ \hline \text { Part time } & 25 \mathrm{hr} & \$ 12 \\ \hline \end{array} $$ The store manager also knows that to make the store run efficiently, the number of full-time employees must be at least 1.25 times the number of part- time employees. a. Determine the number of full-time employees and the number of part-time employees that should be used to minimize the weekly labor cost. b. What is the minimum weekly cost to staff the store under these constraints?

The population \(P(t)\) of a culture of bacteria grows exponentially for the first 72 hr according to the model \(P(t)=P_{0} e^{k t} .\) The variable \(t\) is the time in hours since the culture is started. The population of bacteria is 60,000 after 7 hr. The population grows to 80,000 after 12 hr. a. Determine the constant \(k\) to 3 decimal places. b. Determine the original population \(P_{0}\). Round to the nearest thousand. c. Determine the time required for the population to reach 300,000 . Round to the nearest hour.

The minimum and maximum distances from a point \(P\) to a circle are found using the line determined by the given point and the center of the circle. Given the circle defined by \(x^{2}+y^{2}=9\) and the point \(P(4,5)\), a. Find the point on the circle closest to the point (4,5) . b. Find the point on the circle furthest from the point (4,5) .

Two particles begin at the same point and move at different speeds along a circular path of circumference \(280 \mathrm{ft}\). Moving in opposite directions, they pass in \(10 \mathrm{sec} .\) Moving in the same direction, they pass in \(70 \mathrm{sec} .\) Find the speed of each particle.

Solve the system of equations by using the addition method. (See Examples \(3-4)\) $$ \begin{array}{l} 3 x-7 y=1 \\ 6 x+5 y=-17 \end{array} $$

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