Chapter 7: Problem 46
Solve each system by elimination. $$\begin{aligned}&\frac{x+6}{5}+\frac{2 y-x}{10}=1\\\&\frac{x+2}{4}+\frac{3 y+2}{5}=-3\end{aligned}$$
Short Answer
Expert verified
The solution is \( x = 66 \) and \( y = -34 \).
Step by step solution
01
Simplify the Equations
First, simplify the fractions in each equation to make them easier to work with.Equation 1: \( \frac{x+6}{5} + \frac{2y-x}{10} = 1 \) becomes: Multiply the first term by 2 to have a common denominator: \( \frac{2(x+6)}{10} + \frac{2y-x}{10} = 1 \).Combine under a common denominator: \( \frac{2x + 12 + 2y - x}{10} = 1 \). Simplify: \( \frac{x + 2y + 12}{10} = 1 \).Equation 2: \( \frac{x+2}{4} + \frac{3y+2}{5} = -3 \) becomes: Multiply the first term by 5 and the second term by 4 to have a common denominator of 20: \( \frac{5(x+2)}{20} + \frac{4(3y+2)}{20} = -3 \).Combine under a common denominator: \( \frac{5x + 10 + 12y + 8}{20} = -3 \). Simplify: \( \frac{5x + 12y + 18}{20} = -3 \).
02
Eliminate the Fractions
Clear the fractions by multiplying each equation through by the least common multiple (LCM) of the denominators.Equation 1: The LCM of 10 is 10. Multiply through to get:\( x + 2y + 12 = 10 \).Equation 2: The LCM of 20 is 20. Multiply through to get:\( 5x + 12y + 18 = -60 \).
03
Align the System
Write each equation in standard form where similar terms are aligned.Equation 1: \( x + 2y = -2 \) (we moved 12 to the other side by subtracting it from both sides).Equation 2: \( 5x + 12y = -78 \) (we subtracted 18 from both sides).
04
Eliminate One Variable
Choose a variable to eliminate using the elimination method. Here, we will eliminate \( x \).Multiply the first equation by 5 (coefficient of \( x \) in the second equation) to align \( x \):Equation 1 becomes: \( 5x + 10y = -10 \).Now subtract this result from Equation 2:\( (5x + 12y = -78) - (5x + 10y = -10) \).The \( x \) terms cancel out, resulting in:\( 2y = -68 \).
05
Solve for Remaining Variable
Solve for \( y \):Divide both sides by 2:\( y = -34 \).
06
Solve for the Other Variable
Substitute \( y = -34 \) back into one of the original simplified equations to solve for \( x \). We'll use Equation 1: \( x + 2y = -2 \).Substitute \( y = -34 \):\( x + 2(-34) = -2 \).Simplify:\( x - 68 = -2 \).Add 68 to both sides:\( x = 66 \).
07
Solution Check
Verify the solution by substituting \( x = 66 \) and \( y = -34 \) back into the original equations.For Equation 1: \( \frac{66+6}{5} + \frac{2(-34)-66}{10} = 1 \), this simplifies correctly.For Equation 2: \( \frac{66+2}{4} + \frac{3(-34)+2}{5} = -3 \), this simplifies correctly.Both equations satisfy the solutions, confirming they are correct.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Elimination Method
The elimination method is a fundamental technique used to solve systems of equations, particularly linear equations. This method involves eliminating one of the variables in a system so you can solve for the other variable easily.
- **How it Works**: Start by aligning the equations. You may need to multiply one or both equations by a certain number to ensure one variable has the same coefficient in both equations.
- **Reduction**: Subtract or add the equations to cancel out one variable. This leaves you with a single equation containing only one variable, which is much easier to solve.
- **Example**: Suppose you are given \( x + 2y = -2 \) and \( 5x + 12y = -78 \). To eliminate \( x \), multiply the first equation by 5, resulting in \( 5x + 10y = -10 \). Subtract this new equation from the second to get \( 2y = -68 \).
Solving Fractions
Solving equations with fractions can seem a bit challenging, but it becomes straightforward when you apply the right techniques. A common approach is to eliminate the fractions by finding a common denominator.
- **Identifying the Common Denominator**: Look at all the denominators in your equations. Find the least common multiple (LCM) of these denominators.
- **Clearing Fractions**: Multiply each term of the equation by the LCM. This step transforms the equation into one without fractions, simplifying it significantly.
- **Example**: For the system \( \frac{x+6}{5} + \frac{2y-x}{10} = 1 \) and \( \frac{x+2}{4} + \frac{3y+2}{5} = -3 \), identify the LCMs (10 and 20). Multiply through to remove fractions, simplifying your work.
Linear Equations
Linear equations are equations where each term is either a constant or the product of a constant and a single variable. They form straight lines when graphed.
- **Standard Form**: These equations are commonly expressed as \( ax + by = c \). Each variable is to the first power, and there are no products of variables.
- **Graphing**: When graphed on a coordinate plane, linear equations represent straight lines. The intersection point of two lines is the solution of the system represented by those equations.
- **Example in Systems**: In the system \( x + 2y = -2 \) and \( 5x + 12y = -78 \), we see typical linear equations. Methods such as elimination or substitution are used to find where these lines intersect, revealing the solution.