Not multiplying the equations by the necessary scalars

Oct 13, 2025 by pynkocean.com 37 views

Introduction

Systems of linear equations are a fundamental concept in mathematics, and solving them is a crucial skill for students to master. One of the most effective methods for solving systems of linear equations is the elimination method. In this article, we will explore how Mari can use the elimination method to find the solution to the following system of linear equations:

{ \begin{cases} 2f - 5g = -9 \\ -7f + 3g = 4 \end{cases} \}

What is the Elimination Method?

The elimination method is a technique used to solve systems of linear equations by adding or subtracting the equations to eliminate one of the variables. This method is based on the concept of linear combinations, where we multiply each equation by a scalar and then add or subtract the resulting equations to eliminate one of the variables.

Step 1: Multiply the First Equation by 7

To eliminate the variable f, we need to multiply the first equation by 7. This will give us:

{ 14f - 35g = -63 \}

Step 2: Multiply the Second Equation by 2

To eliminate the variable f, we also need to multiply the second equation by 2. This will give us:

{ -14f + 6g = 8 \}

Step 3: Add the Two Equations

Now that we have multiplied both equations by the necessary scalars, we can add the two equations to eliminate the variable f. This will give us:

{ -29g = -55 \}

Step 4: Solve for g

To solve for g, we can divide both sides of the equation by -29. This will give us:

{ g = \frac{55}{29} \}

Step 5: Substitute g into One of the Original Equations

Now that we have found the value of g, we can substitute it into one of the original equations to solve for f. Let's use the first equation:

{ 2f - 5g = -9 \}

Substituting g = 55/29 into this equation, we get:

{ 2f - 5(\frac{55}{29}) = -9 \}

Simplifying this equation, we get:

{ 2f - \frac{275}{29} = -9 \}

Multiplying both sides of the equation by 29, we get:

{ 58f - 275 = -261 \}

Adding 275 to both sides of the equation, we get:

{ 58f = 14 \}

Dividing both sides of the equation by 58, we get:

{ f = \frac{14}{58} \}

Conclusion

In this article, we have shown how Mari can use the elimination method to solve the following system of linear equations:

{ \begin{cases} 2f - 5g = -9 \\ -7f + 3g = 4 \end{cases} \}

By multiplying the first equation by 7 and the second equation by 2, and then adding the two equations, we were able to eliminate the variable f and solve for g. We then substituted g into one of the original equations to solve for f.

Final Answer

The final answer is: $\boxed{\frac{14}{58}}$

Discussion

The elimination method is a powerful tool for solving systems of linear equations. By multiplying the equations by the necessary scalars and then adding or subtracting the resulting equations, we can eliminate one of the variables and solve for the other variable.

In this example, we multiplied the first equation by 7 and the second equation by 2, and then added the two equations to eliminate the variable f. We then substituted g into one of the original equations to solve for f.

The elimination method is a useful technique to have in your mathematical toolkit, and it can be applied to a wide range of problems. With practice and patience, you can become proficient in using the elimination method to solve systems of linear equations.

Common Mistakes

When using the elimination method, there are several common mistakes to avoid:

Not multiplying the equations by the necessary scalars: Make sure to multiply the equations by the necessary scalars to eliminate one of the variables.
Not adding or subtracting the equations correctly: Make sure to add or subtract the equations correctly to eliminate one of the variables.
Not substituting the value of one variable into the other equation: Make sure to substitute the value of one variable into the other equation to solve for the other variable.

By avoiding these common mistakes, you can ensure that you are using the elimination method correctly and solving systems of linear equations accurately.

Real-World Applications

The elimination method has many real-world applications, including:

Physics and engineering: The elimination method is used to solve systems of linear equations that arise in physics and engineering, such as the motion of objects and the behavior of electrical circuits.
Computer science: The elimination method is used to solve systems of linear equations that arise in computer science, such as the solution of linear programming problems.
Economics: The elimination method is used to solve systems of linear equations that arise in economics, such as the solution of linear programming problems.

Q: What is the elimination method?

A: The elimination method is a technique used to solve systems of linear equations by adding or subtracting the equations to eliminate one of the variables.

Q: How do I know which variable to eliminate?

A: To determine which variable to eliminate, you need to look at the coefficients of the variables in the two equations. If the coefficients of the variables are the same, you can eliminate one of the variables by adding or subtracting the equations. If the coefficients are different, you need to multiply one or both of the equations by a scalar to make the coefficients the same.

Q: What is a scalar?

A: A scalar is a number that is multiplied by a variable or an equation. In the elimination method, you need to multiply one or both of the equations by a scalar to make the coefficients of the variables the same.

Q: How do I multiply an equation by a scalar?

A: To multiply an equation by a scalar, you need to multiply each term in the equation by the scalar. For example, if you want to multiply the equation 2x + 3y = 4 by 2, you would get 4x + 6y = 8.

Q: What is the difference between adding and subtracting equations?

A: When you add two equations, you are combining the two equations to eliminate one of the variables. When you subtract one equation from another, you are combining the two equations to eliminate one of the variables, but in the opposite direction.

Q: How do I know which equation to add or subtract?

A: To determine which equation to add or subtract, you need to look at the coefficients of the variables in the two equations. If the coefficients of the variables are the same, you can add the equations to eliminate one of the variables. If the coefficients are different, you need to multiply one or both of the equations by a scalar to make the coefficients the same.

Q: What if I have a system of linear equations with three variables?

A: If you have a system of linear equations with three variables, you can use the elimination method to solve the system by eliminating one of the variables and then solving for the other two variables.

Q: Can I use the elimination method to solve a system of linear equations with more than three variables?

A: Yes, you can use the elimination method to solve a system of linear equations with more than three variables. However, the process becomes more complex and may require the use of matrices and other advanced techniques.

Q: What are some common mistakes to avoid when using the elimination method?

A: Some common mistakes to avoid when using the elimination method include:

Not multiplying the equations by the necessary scalars
Not adding or subtracting the equations correctly
Not substituting the value of one variable into the other equation
Not checking the solution to make sure it is consistent with the original equations

Q: How can I practice using the elimination method?

A: You can practice using the elimination method by working through examples and exercises in a textbook or online resource. You can also try solving systems of linear equations using the elimination method and then checking your solution to make sure it is correct.

Q: What are some real-world applications of the elimination method?

A: The elimination method has many real-world applications, including:

Physics and engineering: The elimination method is used to solve systems of linear equations that arise in physics and engineering, such as the motion of objects and the behavior of electrical circuits.
Computer science: The elimination method is used to solve systems of linear equations that arise in computer science, such as the solution of linear programming problems.
Economics: The elimination method is used to solve systems of linear equations that arise in economics, such as the solution of linear programming problems.

Conclusion

The elimination method is a powerful tool for solving systems of linear equations. By adding or subtracting the equations to eliminate one of the variables, you can solve for the other variable. With practice and patience, you can become proficient in using the elimination method to solve systems of linear equations.