Solve The System Of Equations Using Substitution.$\[ \begin{align*} 6r + 7s &= -1 \\ 2r + 4s &= -12 \end{align*} \\]A. \[$(-4, -8)\$\] B. \[$(-8, -4)\$\] C. \[$(-7, 8)\$\] D. \[$(8, -7)\$\]

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Introduction

Solving systems of equations is a fundamental concept in mathematics, and it is essential to understand various methods to solve them. One of the most popular methods is substitution, which involves solving one equation for a variable and then substituting that expression into the other equation. In this article, we will explore how to solve systems of equations using substitution.

What is Substitution?

Substitution is a method of solving systems of equations by solving one equation for a variable and then substituting that expression into the other equation. This method is useful when one of the equations is easily solvable for a variable. The basic steps involved in substitution are:

  1. Solve one equation for a variable.
  2. Substitute the expression into the other equation.
  3. Solve the resulting equation for the other variable.
  4. Substitute the value of the second variable back into one of the original equations to find the value of the first variable.

Step-by-Step Guide to Solving Systems of Equations Using Substitution

Let's consider the following system of equations:

{ \begin{align*} 6r + 7s &= -1 \\ 2r + 4s &= -12 \end{align*} \}

To solve this system using substitution, we can follow these steps:

Step 1: Solve One Equation for a Variable

We can solve the second equation for rr:

2r=−12−4s2r = -12 - 4s

r=−12−4s2r = \frac{-12 - 4s}{2}

r=−6−2sr = -6 - 2s

Step 2: Substitute the Expression into the Other Equation

Now, we can substitute the expression for rr into the first equation:

6(−6−2s)+7s=−16(-6 - 2s) + 7s = -1

Step 3: Solve the Resulting Equation for the Other Variable

Expanding the equation, we get:

−36−12s+7s=−1-36 - 12s + 7s = -1

Combine like terms:

−36−5s=−1-36 - 5s = -1

Add 36 to both sides:

−5s=35-5s = 35

Divide by -5:

s=−7s = -7

Step 4: Substitute the Value of the Second Variable Back into One of the Original Equations

Now that we have the value of ss, we can substitute it back into one of the original equations to find the value of rr. Let's use the second equation:

2r+4s=−122r + 4s = -12

Substitute s=−7s = -7:

2r+4(−7)=−122r + 4(-7) = -12

Simplify:

2r−28=−122r - 28 = -12

Add 28 to both sides:

2r=162r = 16

Divide by 2:

r=8r = 8

Conclusion

In this article, we have learned how to solve systems of equations using substitution. We have followed a step-by-step guide to solve the system of equations:

{ \begin{align*} 6r + 7s &= -1 \\ 2r + 4s &= -12 \end{align*} \}

The solution to the system is r=8r = 8 and s=−7s = -7. This method is useful when one of the equations is easily solvable for a variable.

Final Answer

The final answer is (8,−7)\boxed{(8, -7)}.

Discussion

This method is useful when one of the equations is easily solvable for a variable. However, it may not be the most efficient method for solving systems of equations, especially when the equations are complex. In such cases, other methods like elimination or matrices may be more suitable.

Example Problems

Here are some example problems to practice solving systems of equations using substitution:

  1. {

\begin{align*} 3x + 2y &= 5 \ x + 4y &= 3 \end{align*} }$ 2. ${ \begin{align*} 2x + 3y &= 7 \ x + 2y &= 4 \end{align*} }$ 3. ${ \begin{align*} 4x + 3y &= 9 \ 2x + 5y &= 11 \end{align*} }$

Tips and Tricks

Here are some tips and tricks to help you solve systems of equations using substitution:

  1. Choose the equation that is easily solvable for a variable.
  2. Substitute the expression into the other equation carefully.
  3. Simplify the resulting equation to make it easier to solve.
  4. Check your solution by substituting the values back into the original equations.

By following these steps and tips, you can become proficient in solving systems of equations using substitution.

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Introduction

In our previous article, we explored how to solve systems of equations using substitution. This method is a powerful tool for solving systems of linear equations, and it's essential to understand how to apply it correctly. In this article, we'll answer some frequently asked questions about solving systems of equations using substitution.

Q&A

Q: What is the first step in solving a system of equations using substitution?

A: The first step is to choose one of the equations and solve it for one of the variables. This will give you an expression that you can substitute into the other equation.

Q: How do I choose which equation to solve first?

A: Choose the equation that is easiest to solve for one of the variables. If one equation has a coefficient of 1 for one of the variables, it's usually easier to solve for that variable.

Q: What if I have two equations with the same variable on one side of each equation?

A: In this case, you can add or subtract the equations to eliminate one of the variables. This is called the elimination method.

Q: Can I use substitution with non-linear equations?

A: No, substitution is typically used with linear equations. If you have a non-linear equation, you may need to use a different method, such as graphing or numerical methods.

Q: How do I know if I've found the correct solution?

A: To check your solution, substitute the values back into both original equations. If the equations are true, then you've found the correct solution.

Q: What if I get a system of equations with no solution?

A: If you get a system of equations with no solution, it means that the equations are inconsistent. This can happen if the equations are contradictory, such as 2x + 3y = 5 and 2x + 3y = 10.

Q: Can I use substitution with systems of equations with more than two variables?

A: Yes, you can use substitution with systems of equations with more than two variables. However, it may be more complicated and require more steps.

Common Mistakes to Avoid

When solving systems of equations using substitution, there are several common mistakes to avoid:

  1. Not checking the solution: Always check your solution by substituting the values back into both original equations.
  2. Not simplifying the equations: Make sure to simplify the equations as much as possible to avoid errors.
  3. Not choosing the correct equation to solve first: Choose the equation that is easiest to solve for one of the variables.
  4. Not substituting the expression correctly: Make sure to substitute the expression into the other equation carefully.

Tips and Tricks

Here are some additional tips and tricks to help you solve systems of equations using substitution:

  1. Use a systematic approach: Break down the problem into smaller steps and follow a systematic approach.
  2. Check your work: Always check your solution by substituting the values back into both original equations.
  3. Use a calculator or computer: If you're having trouble solving the system, try using a calculator or computer to check your work.
  4. Practice, practice, practice: The more you practice solving systems of equations using substitution, the more comfortable you'll become with the method.

Conclusion

Solving systems of equations using substitution is a powerful tool for solving systems of linear equations. By following the steps outlined in this article and avoiding common mistakes, you can become proficient in solving systems of equations using substitution. Remember to check your solution, simplify the equations, and choose the correct equation to solve first. With practice, you'll become more comfortable with this method and be able to solve systems of equations with ease.

Final Answer

The final answer is (8,−7)\boxed{(8, -7)}.

Discussion

This method is useful when one of the equations is easily solvable for a variable. However, it may not be the most efficient method for solving systems of equations, especially when the equations are complex. In such cases, other methods like elimination or matrices may be more suitable.

Example Problems

Here are some example problems to practice solving systems of equations using substitution:

  1. {

\begin{align*} 3x + 2y &= 5 \ x + 4y &= 3 \end{align*} }$ 2. ${ \begin{align*} 2x + 3y &= 7 \ x + 2y &= 4 \end{align*} }$ 3. ${ \begin{align*} 4x + 3y &= 9 \ 2x + 5y &= 11 \end{align*} }$

Tips for Teachers

Here are some tips for teachers to help students learn how to solve systems of equations using substitution:

  1. Use visual aids: Use graphs, charts, and diagrams to help students visualize the problem.
  2. Provide practice problems: Provide students with a variety of practice problems to help them become proficient in solving systems of equations using substitution.
  3. Encourage students to check their work: Encourage students to check their solution by substituting the values back into both original equations.
  4. Use technology: Use technology, such as calculators or computers, to help students check their work and visualize the problem.

By following these tips and tricks, you can help your students become proficient in solving systems of equations using substitution.