Multiplying Equation 1 by 1 and Equation 2 by 4

Oct 13, 2025 by wbrum.org 138 views

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Introduction

The elimination method is a powerful technique used to solve systems of linear equations. It involves adding or subtracting equations to eliminate one of the variables, making it easier to solve for the remaining variables. In this article, we will use the elimination method to solve a system of two linear equations with two variables.

The System of Equations

We are given the following system of equations:

Equation 1

8x + 4z = 84

Equation 2

2x - 6z = 14

Step 1: Multiply the Equations by Necessary Multiples

To eliminate one of the variables, we need to make the coefficients of either x or z the same in both equations. We can do this by multiplying the equations by necessary multiples.

Multiplying Equation 1 by 1 and Equation 2 by 4

Multiplying Equation 1 by 1 and Equation 2 by 4 gives us:

Equation 1 (Multiplied by 1)

8x + 4z = 84

Equation 2 (Multiplied by 4)

8x - 24z = 56

Step 2: Add or Subtract the Equations

Now that we have the same coefficient for x in both equations, we can add or subtract the equations to eliminate x.

Adding Equation 1 and Equation 2

Adding Equation 1 and Equation 2 gives us:

8x + 4z + 8x - 24z = 84 + 56

Simplifying the equation gives us:

16x - 20z = 140

Step 3: Solve for z

Now that we have eliminated x, we can solve for z.

Rearranging the Equation

Rearranging the equation to isolate z gives us:

-20z = 140 - 16x

Dividing by -20

Dividing both sides of the equation by -20 gives us:

z = \frac{140 - 16x}{-20}

Simplifying the Equation

Simplifying the equation gives us:

z = -7 + \frac{4x}{5}

Step 4: Substitute the Value of z into One of the Original Equations

Now that we have the value of z, we can substitute it into one of the original equations to solve for x.

Substituting z into Equation 1

Substituting z into Equation 1 gives us:

8x + 4(-7 + \frac{4x}{5}) = 84

Simplifying the Equation

Simplifying the equation gives us:

8x - 28 + \frac{16x}{5} = 84

Multiplying the Equation by 5

Multiplying the equation by 5 gives us:

40x - 140 + 16x = 420

Combining Like Terms

Combining like terms gives us:

56x - 140 = 420

Adding 140 to Both Sides

Adding 140 to both sides of the equation gives us:

56x = 560

Dividing by 56

Dividing both sides of the equation by 56 gives us:

x = \frac{560}{56}

Simplifying the Equation

Simplifying the equation gives us:

x = 10

Step 5: Find the Value of z

Now that we have the value of x, we can find the value of z.

Substituting x into the Equation for z

Substituting x into the equation for z gives us:

z = -7 + \frac{4(10)}{5}

Simplifying the Equation

Simplifying the equation gives us:

z = -7 + 8

Simplifying Further

Simplifying further gives us:

z = 1

Conclusion

In this article, we used the elimination method to solve a system of two linear equations with two variables. We multiplied the equations by necessary multiples, added or subtracted the equations to eliminate one of the variables, and then solved for the remaining variable. We found that the value of x is 10 and the value of z is 1.

Example Use Case

The elimination method can be used to solve systems of linear equations in a variety of real-world applications, such as:

Physics: To solve problems involving motion, forces, and energies.
Engineering: To design and optimize systems, such as electrical circuits and mechanical systems.
Economics: To model and analyze economic systems, such as supply and demand.

Tips and Variations

Use the elimination method when the coefficients of one variable are the same in both equations.
Multiply the equations by necessary multiples to make the coefficients of one variable the same.
Add or subtract the equations to eliminate one of the variables.
Solve for the remaining variable using algebraic manipulations.

By following these steps and tips, you can use the elimination method to solve systems of linear equations and apply it to a variety of real-world applications.

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Q: What is the elimination method?

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

Q: When should I use the elimination method?

A: You should use the elimination method when the coefficients of one variable are the same in both equations.

Q: How do I multiply the equations by necessary multiples?

A: To multiply the equations by necessary multiples, you need to make the coefficients of one variable the same in both equations. You can do this by multiplying the equations by the same number.

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

A: Adding equations involves adding the two equations together, while subtracting equations involves subtracting one equation from the other.

Q: How do I solve for the remaining variable?

A: To solve for the remaining variable, you need to isolate the variable by performing algebraic manipulations.

Q: Can I use the elimination method to solve systems of equations with more than two variables?

A: Yes, you can use the elimination method to solve systems of equations with more than two variables. However, you need to be careful when multiplying the equations by necessary multiples to avoid creating fractions.

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 necessary multiples
Not adding or subtracting the equations correctly
Not isolating the remaining variable
Not checking for fractions

Q: Can I use the elimination method to solve systems of equations with fractions?

A: Yes, you can use the elimination method to solve systems of equations with fractions. However, you need to be careful when multiplying the equations by necessary multiples to avoid creating fractions.

Q: How do I check my work when using the elimination method?

A: To check your work when using the elimination method, you need to substitute the values of the variables back into the original equations and verify that they are true.

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

A: Some real-world applications of the elimination method include:

Physics: To solve problems involving motion, forces, and energies.
Engineering: To design and optimize systems, such as electrical circuits and mechanical systems.
Economics: To model and analyze economic systems, such as supply and demand.

Q: Can I use the elimination method to solve systems of equations with non-linear equations?

A: No, the elimination method is only used to solve systems of linear equations. If you have a system of non-linear equations, you need to use a different method, such as substitution or graphing.

Q: How do I choose between the elimination method and other methods, such as substitution or graphing?

A: To choose between the elimination method and other methods, you need to consider the type of equations you are working with and the variables you are trying to solve for. The elimination method is best used when the coefficients of one variable are the same in both equations.

Q: Can I use the elimination method to solve systems of equations with complex numbers?

A: Yes, you can use the elimination method to solve systems of equations with complex numbers. However, you need to be careful when multiplying the equations by necessary multiples to avoid creating fractions.

Q: How do I extend the elimination method to solve systems of equations with more than two variables?

A: To extend the elimination method to solve systems of equations with more than two variables, you need to use the same steps as before, but with more variables. You need to multiply the equations by necessary multiples, add or subtract the equations to eliminate one of the variables, and then solve for the remaining variables.

Q: Can I use the elimination method to solve systems of equations with matrices?

A: Yes, you can use the elimination method to solve systems of equations with matrices. However, you need to be careful when multiplying the matrices by necessary multiples to avoid creating fractions.

Q: How do I check my work when using the elimination method with matrices?

A: To check your work when using the elimination method with matrices, you need to substitute the values of the variables back into the original equations and verify that they are true.

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

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

Not multiplying the matrices by necessary multiples
Not adding or subtracting the matrices correctly
Not isolating the remaining variable
Not checking for fractions

Q: Can I use the elimination method to solve systems of equations with determinants?

A: Yes, you can use the elimination method to solve systems of equations with determinants. However, you need to be careful when multiplying the determinants by necessary multiples to avoid creating fractions.

Q: How do I check my work when using the elimination method with determinants?

A: To check your work when using the elimination method with determinants, you need to substitute the values of the variables back into the original equations and verify that they are true.

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

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

Not multiplying the determinants by necessary multiples
Not adding or subtracting the determinants correctly
Not isolating the remaining variable
Not checking for fractions

By following these FAQs, you can better understand the elimination method and how to use it to solve systems of linear equations.