Check if the equations are equivalent

Oct 13, 2025 by wbrum.org 124 views

Introduction

Systems of equations are a fundamental concept in mathematics, and solving them is a crucial skill for students and professionals alike. In this article, we will explore a system of two linear equations and provide a step-by-step guide on how to solve it. We will also answer a series of questions related to the system, including how to eliminate the x-terms when multiplying the second equation.

The System of Equations

The system of equations we will be working with is:

${ \begin{array}{r} 4x - 9y = 7 \\ -2x + 3y = 4 \end{array} }$

Question 1: Eliminating the x-terms

To eliminate the x-terms when multiplying the second equation, we need to find a number that, when multiplied by the second equation, will make the coefficient of x in the resulting equation equal to the coefficient of x in the first equation. In other words, we need to find a number that will make the x-terms cancel out.

To do this, we can multiply the second equation by a number that will make the coefficient of x in the resulting equation equal to 4, which is the coefficient of x in the first equation. Let's call this number k.

Multiplying the second equation by k, we get:

${ -2kx + 3ky = 4k }$

We want the coefficient of x in this equation to be equal to 4, so we can set up the following equation:

${ -2k = 4 }$

Solving for k, we get:

${ k = -2 }$

So, to eliminate the x-terms when multiplying the second equation, we need to multiply it by -2.

Question 2: Multiplying the Second Equation

Now that we know we need to multiply the second equation by -2, let's do it:

${ -2(-2x + 3y) = -2(4) }$

Expanding the left-hand side, we get:

${ 4x - 6y = -8 }$

Question 3: Adding the Two Equations

Now that we have eliminated the x-terms in the second equation, we can add the two equations to eliminate the y-terms:

${ (4x - 9y) + (4x - 6y) = 7 + (-8) }$

Simplifying the left-hand side, we get:

${ 8x - 15y = -1 }$

Question 4: Solving for x

Now that we have eliminated the y-terms, we can solve for x by multiplying the first equation by 15 and the second equation by 9:

${ 15(4x - 9y) = 15(7) }$ ${ 9(8x - 15y) = 9(-1) }$

Expanding the left-hand side of both equations, we get:

${ 60x - 135y = 105 }$ ${ 72x - 135y = -9 }$

Subtracting the second equation from the first, we get:

${ -12x = 114 }$

Dividing both sides by -12, we get:

${ x = -\frac{114}{12} }$

Simplifying, we get:

${ x = -\frac{19}{2} }$

Question 5: Solving for y

Now that we have solved for x, we can substitute the value of x into one of the original equations to solve for y. Let's use the first equation:

${ 4x - 9y = 7 }$

Substituting x = -19/2, we get:

${ 4(-\frac{19}{2}) - 9y = 7 }$

Simplifying the left-hand side, we get:

${ -38 - 9y = 7 }$

Adding 38 to both sides, we get:

${ -9y = 45 }$

Dividing both sides by -9, we get:

${ y = -\frac{45}{9} }$

Simplifying, we get:

${ y = -5 }$

Conclusion

Introduction

In our previous article, we explored a system of two linear equations and provided a step-by-step guide on how to solve it. We also answered a series of questions related to the system, including how to eliminate the x-terms when multiplying the second equation. In this article, we will continue to provide a Q&A guide on solving systems of equations.

Q&A

Q: What is a system of equations?

A: A system of equations is a set of two or more equations that are related to each other. Each equation in the system is a statement that two expressions are equal.

Q: What are the different methods for solving systems of equations?

A: There are several methods for solving systems of equations, including:

Substitution method: This method involves solving one equation for one variable and then substituting that expression into the other equation.
Elimination method: This method involves adding or subtracting the equations to eliminate one variable.
Graphing method: This method involves graphing the equations on a coordinate plane and finding the point of intersection.

Q: How do I choose which method to use?

A: The choice of method depends on the type of equations and the variables involved. If the equations are linear and have two variables, the substitution or elimination method is usually the best choice. If the equations are non-linear or have more than two variables, the graphing method may be more suitable.

Q: What is the difference between a dependent and independent system?

A: A dependent system is a system of equations where the equations are equivalent and represent the same line or curve. A independent system is a system of equations where the equations are not equivalent and represent different lines or curves.

Q: How do I determine if a system is dependent or independent?

A: To determine if a system is dependent or independent, you can use the following methods:

Check if the equations are equivalent: If the equations are equivalent, the system is dependent. If the equations are not equivalent, the system is independent.
Graph the equations: If the graphs of the equations intersect at a single point, the system is dependent. If the graphs do not intersect, the system is independent.

Q: What is the purpose of solving a system of equations?

A: The purpose of solving a system of equations is to find the values of the variables that satisfy all the equations in the system. This can be useful in a variety of applications, such as:

Physics and engineering: Solving systems of equations can help to model real-world problems and make predictions about the behavior of physical systems.
Economics: Solving systems of equations can help to model economic systems and make predictions about the behavior of economic variables.
Computer science: Solving systems of equations can help to model complex systems and make predictions about the behavior of computer systems.

Q: What are some common mistakes to avoid when solving systems of equations?

A: Some common mistakes to avoid when solving systems of equations include:

Not checking for equivalent equations: Make sure to check if the equations are equivalent before solving the system.
Not using the correct method: Choose the correct method for solving the system based on the type of equations and variables involved.
Not checking for dependent or independent systems: Make sure to check if the system is dependent or independent before solving it.

Conclusion

In this article, we have provided a Q&A guide on solving systems of equations. We have covered topics such as the different methods for solving systems of equations, how to choose which method to use, and common mistakes to avoid. We hope that this guide has been helpful in providing a better understanding of solving systems of equations.