Chapter 1: Problem 36
Solve the following system for \(x, y,\) and \(z\) $$\begin{aligned}\frac{1}{x}+\frac{2}{y}-\frac{4}{z} &=1 \\\\\frac{2}{x}+\frac{3}{y}+\frac{8}{z} &=0 \\\\-\frac{1}{x}+\frac{9}{y}+\frac{10}{z} &=5 \end{aligned}$$
Short Answer
Expert verified
The solution is \(x = -\frac{13}{7}\), \(y = \frac{91}{54}\), \(z = -\frac{91}{8}\).
Step by step solution
01
Express Each Fraction Separately
Given the system of equations:\[ \frac{1}{x} + \frac{2}{y} - \frac{4}{z} = 1 \]\[ \frac{2}{x} + \frac{3}{y} + \frac{8}{z} = 0 \]\[ -\frac{1}{x} + \frac{9}{y} + \frac{10}{z} = 5 \]Let's denote \( a = \frac{1}{x} \), \( b = \frac{1}{y} \), and \( c = \frac{1}{z} \). The system becomes:\[ a + 2b - 4c = 1 \]\[ 2a + 3b + 8c = 0 \]\[ -a + 9b + 10c = 5 \].
02
Solve the System of Linear Equations
We will solve the linear system in terms of \(a\), \(b\), and \(c\):1. Start with the first two equations: \[ a + 2b - 4c = 1 \] \[ 2a + 3b + 8c = 0 \] Multiply the first equation by 2: \[ 2a + 4b - 8c = 2 \] Subtract the second equation from the modified first equation: \[ (2a + 4b - 8c) - (2a + 3b + 8c) = 2 - 0 \] Simplify to get: \[ b - 16c = 2 \] (Equation 4)2. Use Equations 1 and 3: \[ a + 2b - 4c = 1 \] \[ -a + 9b + 10c = 5 \] Add these equations: \[ 11b + 6c = 6 \] (Equation 5).3. Use Equations 4 and 5 to solve for \(b\) and \(c\): First rearrange Equation 5: \[ b = 16c + 2 \] Substitute into Equation 5: \[ 11(16c + 2) + 6c = 6 \] \[ 176c + 22 + 6c = 6 \] \[ 182c = -16 \] \[ c = -\frac{8}{91} \].
03
Substitute and Solve for Remaining Variables
Substitute \(c = -\frac{8}{91}\) back into \(b = 16c + 2\):\[ b = 16\left(-\frac{8}{91}\right) + 2 \]\[ b = -\frac{128}{91} + 2 \]\[ b = -\frac{128}{91} + \frac{182}{91} \]\[ b = \frac{54}{91} \].Now substitute \(b\) and \(c\) into one of the original equations to find \(a\). Use Equation 1:\[ a + 2\left(\frac{54}{91}\right) - 4\left(-\frac{8}{91}\right) = 1 \]\[ a + \frac{108}{91} + \frac{32}{91} = 1 \]\[ a + \frac{140}{91} = 1 \]\[ a = 1 - \frac{140}{91} \]\[ a = \frac{91}{91} - \frac{140}{91} \]\[ a = -\frac{49}{91} \].
04
Solve for Original Variables \(x\), \(y\), and \(z\)
We have \(a = \frac{1}{x} = -\frac{49}{91}\), \(b = \frac{1}{y} = \frac{54}{91}\), and \(c = \frac{1}{z} = -\frac{8}{91}\).Thus, solve for \(x\), \(y\), and \(z\):- \( x = -\frac{91}{49} = -\frac{13}{7} \)- \( y = \frac{91}{54} \)- \( z = -\frac{91}{8} \).
05
Verification
Substitute the values back into the original equations to verify:1. \( \frac{1}{x} + \frac{2}{y} - \frac{4}{z} = 1 \) Produces: \( -\frac{49}{91} + 2(\frac{54}{91}) - 4(-\frac{8}{91}) = \frac{-49+108+32}{91} = 91/91 = 1 \)2. \( \frac{2}{x} + \frac{3}{y} + \frac{8}{z} = 0 \) Produces: \( 2(-\frac{49}{91}) + 3(\frac{54}{91}) + 8(-\frac{8}{91}) = \frac{-98+162-64}{91} = 0 \)3. \( -\frac{1}{x} + \frac{9}{y} + \frac{10}{z} = 5 \) Produces: \( \frac{49}{91} + 9(\frac{54}{91}) + 10(-\frac{8}{91}) = \frac{49+486-80}{91} = 5 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Variable Substitution
When solving a system of linear equations, sometimes terms are complex, like those involving fractions. We can simplify these by using a process called **variable substitution**.
In this method, we substitute complex fractional terms with simpler variables. For example, if you have an equation with sums like \( \frac{1}{x} \), \( \frac{2}{y} \), and \( \frac{4}{z} \), you can set these fractions equal to other variables.
Here's how it's done in our exercise:
In this method, we substitute complex fractional terms with simpler variables. For example, if you have an equation with sums like \( \frac{1}{x} \), \( \frac{2}{y} \), and \( \frac{4}{z} \), you can set these fractions equal to other variables.
Here's how it's done in our exercise:
- Set \( a = \frac{1}{x} \)
- Set \( b = \frac{1}{y} \)
- Set \( c = \frac{1}{z} \)
Solution Verification
After calculating the values of variables from a system of equations, it's crucial to verify if they actually solve the original equations. **Solution verification** ensures accuracy and helps catch any potential mistakes in your calculations.
In our problem, we found \( x = -\frac{13}{7}, y = \frac{91}{54}, z = -\frac{91}{8} \). To verify the solution, substitute these values back into the original set of equations:
In our problem, we found \( x = -\frac{13}{7}, y = \frac{91}{54}, z = -\frac{91}{8} \). To verify the solution, substitute these values back into the original set of equations:
- Check the equation \( \frac{1}{x} + \frac{2}{y} - \frac{4}{z} = 1 \). With the values for \( x, y, \) and \( z \), compute each term.
- Do the same for \( \frac{2}{x} + \frac{3}{y} + \frac{8}{z} = 0 \).
- Finally, validate \( -\frac{1}{x} + \frac{9}{y} + \frac{10}{z} = 5 \).
Fractional Equations
Sometimes, equations like these involve fractions, making them tricky to solve. **Fractional equations** are equations where variables appear in the denomination. Solving these equations typically requires clearing the fractions to simplify the problem.
Here's how to manage them:
Here's how to manage them:
- Commonly, you multiply every term by a common denominator to eliminate fractions.
- For example, from \( \frac{1}{x} + \frac{2}{y} - \frac{4}{z} = 1 \), it's easier if expressed without fractions.
- By using variable substitution, as we did by letting \( \frac{1}{x} = a \), these equations transform into simpler linear equations.