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RS Aggarwal Solutions Class 10 Chapter 3 - Linear Equations in two variables (Ex 3I) Exercise 3.9

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Download Free PDF of RS Aggarwal Solutions Class 10 Chapter 3 - Linear Equations in Two Variables (Ex 3I) Exercise 3.9 Available on Vedantu

Free PDF download of RS Aggarwal Solutions Class 10 Chapter 3 - Linear Equations in two variables (Ex 3I) Exercise 3.9 solved by Expert Mathematics Teachers on Vedantu.com. All Ex 3.9 Questions with Solutions for Class 10 Maths RS Aggarwal to help you to revise complete Syllabus and Score More marks. Register for online coaching for IIT JEE (Mains & Advanced) and other Engineering entrance exams. Every NCERT Solution is provided to make the study simple and interesting on Vedantu. Register Online for Class 10 Science tuition on Vedantu.com to score more marks in CBSE board examination.

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Linear Equations in Two Variables

A system of equations can be called the Linear Equations in two variables if they have either a unique solution, no solution or infinitely many solutions. A system of Linear Equations may have ‘n’ number of variables. While we solve the Linear Equations with n number of variables, there must be n equations to solve for the values of the variables. The set of solutions that are obtained on solving these Linear Equations is a straight line and Linear Equations in two variables are the algebraic equations which are of the form y = mx + y where m is the slope and y is the y intercept of the coordinates. These are equations of the first order. 

Graphical Method

  • Step 1: To solve a system of Linear Equations in two variables, we represent each of the equations in a standard graph.

  • Step 2: To represent a  graph of the given equation, we first convert it to the form of y=mx+b by solving the given equation for y.

  • Step 3: Then, we substitute the values of x as 0, 1, 2, 3, and so on to find the corresponding values of y, vice-versa.

  • Step 4: Identify the point where both the lines meet.

  • Step 5: The point of intersection of both the lines is the solution of the given system of Linear Equations in two variables. 

But, in some cases, both lines may not always intersect. Sometimes they may be parallel to each other. In that case, the system of Linear Equations in two variables will have no solution. In some of the other cases, both lines coincide with each other. In those cases, each point on that particular line is a solution of the given system and hence, the given system has infinitely many numbers of solutions. If the system has a solution, then it is said to be a consistent system; otherwise, it is said to be an inconsistent system. We can identify a system of Linear Equations in two variables if the equations that are expressed in the form ax+by+ c = 0, which consist of two variables x and y and the highest degree of the given equation is 1.

Substitution Method

  • Step 1: Solve one of the given equations for one variable.

  • Step 2: Then, substitute this variable into the other equation to get an equation in terms of a single variable.

  • Step 3: Solve this equation for getting the next variable.

  • Step 4: Then, substitute it in any of the equations to get the value of another variable.

Elimination Method

  • Step 1: Arrange the given equations in the standard form ax+by+c=0 or ax+by=c.

  • Step 2: Check all possibilities of adding and subtracting the equations which would result in the cancellation of a variable.

  • Step 3: If it does not, multiply one or both the equations by either the coefficient of x or coefficient of y, so that their addition or subtraction would result in the cancellation of any one of the variables.

  • Step 4: Solve the resulting equation with one variable.

  • Step 5: Substitute it in any given equation to get the value of another variable.

Graphical Representation of Linear Equations in Two Variables

We can represent the Linear Equations in two variables graphically using the following steps:

  • Step 1: Linear Equations in two variables can be represented graphically by graphing each equation by converting it to the form y=mx+b by solving the equation for the y variable.

  • Step 2: Identify the points at which both of the lines are intersecting.

  • Step 3: The point of intersection is the solution of the given system of the Linear Equations in two variables.

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FAQs on RS Aggarwal Solutions Class 10 Chapter 3 - Linear Equations in two variables (Ex 3I) Exercise 3.9

1. How do the step-by-step RS Aggarwal Solutions for Chapter 3 help in preparing for the Class 10 board exams?

Vedantu’s RS Aggarwal Solutions for Chapter 3, Linear Equations in Two Variables, are curated by subject matter experts to align with the latest CBSE 2025-26 syllabus. They help in exam preparation by:

  • Providing a clear, step-by-step methodology for solving every problem in Exercise 3.9.

  • Helping students understand how to translate complex word problems into algebraic equations.

  • Reinforcing the correct application of methods like Elimination and Substitution, which are crucial for scoring full marks.

  • Highlighting common areas where students might make mistakes, ensuring better accuracy and time management during the exam.

2. What is the standard form of a pair of linear equations in two variables as per the Class 10 syllabus?

The standard form for a pair of linear equations in two variables, x and y, is:

a₁x + b₁y + c₁ = 0

a₂x + b₂y + c₂ = 0

Here, a₁, b₁, c₁, a₂, b₂, and c₂ are real numbers, and it is important that a₁² + b₁² ≠ 0 and a₂² + b₂² ≠ 0. This form is essential for applying algebraic methods and determining the nature of the solution.

3. What are the conditions for a pair of linear equations to have a unique solution, no solution, or infinitely many solutions?

For a pair of linear equations a₁x + b₁y + c₁ = 0 and a₂x + b₂y + c₂ = 0, the nature of the solution depends on the ratio of their coefficients:

  • Unique Solution: If a₁/a₂ ≠ b₁/b₂. The lines representing the equations intersect at exactly one point.

  • No Solution: If a₁/a₂ = b₁/b₂ ≠ c₁/c₂. The lines are parallel and never intersect.

  • Infinitely Many Solutions: If a₁/a₂ = b₁/b₂ = c₁/c₂. The lines are coincident, meaning they are the same line.

4. When solving problems from RS Aggarwal Chapter 3, when is it better to use the elimination method over the substitution method?

Choosing the right method can save time and reduce errors. Here’s a simple guide:

  • Use the elimination method when the coefficients of one of the variables (either x or y) in both equations are the same, opposites, or can be easily made the same by multiplying one or both equations by a small integer. This method is generally faster for such cases.

  • Use the substitution method when one of the variables in either equation has a coefficient of 1 or -1, making it easy to express that variable in terms of the other without creating complex fractions.

5. Why is it necessary to convert word problems into a pair of linear equations before solving them?

Converting word problems into a pair of linear equations is a crucial first step because it translates a real-world scenario into a structured mathematical format. This process helps to:

  • Identify the unknowns and assign variables (like x and y) to them.

  • Establish relationships between these unknowns based on the conditions given in the problem.

  • Create a systematic framework that allows for the application of proven algebraic methods like substitution or elimination to find a precise and verifiable solution.

Without this step, solving complex problems with multiple conditions would be confusing and prone to errors.

6. How can you check if your solution (x, y) for a system of linear equations from Exercise 3.9 is correct?

To verify the correctness of your solution for a pair of linear equations, you must substitute the values of x and y back into both of the original equations. Your solution is correct only if it satisfies both equations simultaneously. If the values make the left-hand side (LHS) equal to the right-hand side (RHS) for both equations, the solution is verified.

7. What are some common mistakes to avoid while solving linear equations from RS Aggarwal Class 10 Chapter 3?

Students often make a few common mistakes while solving problems in this chapter. Be careful to avoid the following:

  • Sign Errors: Incorrectly handling negative signs during addition, subtraction, or transposition of terms is the most frequent error.

  • Incorrect Equation Formulation: Misinterpreting the conditions of a word problem and setting up the wrong initial equations.

  • Calculation Mistakes: Simple arithmetic errors when multiplying equations or substituting values.

  • Incomplete Solution: Finding the value of only one variable (e.g., x) and forgetting to solve for the second variable (y).