[Maths Class Notes] on Pair of Linear Equations in Two Variables Pdf for Exam

Whenever any equation is represented by ax + by + c where x and y are two variables, it is known as a linear equation consisting of two variables. The values of a, b, and c here is not equal to zero and are real numbers. On the other hand, when two such linear equations have the same set of variables, they are known as the pair of linear equations in two variables. Usually, when we solve a pair of linear equations, we get a point or set of points on the coordinate plane as a solution. The line on which the point lies is represented by the equation. The third chapter of class 10 mathematics is about how to solve the following pair of linear equations. The chapter is divided into seven parts with six exercises. The NCERT solutions will help you to understand the sums of this chapter for your examinations.

 

Pair of Linear Equations in Two Variables Solutions

The first part that you will learn in this chapter is the introduction, followed by the graphical representation of a pair of linear equations. The next part will be on solving these linear equations by applying various methods. The chapter discusses in detail, how to solve a pair of linear equations in two variables. In junior classes, we have learned how to solve one variable and one equation system. That was quite easy, but now we have two variables and two-equation methods. Of course, we need two different equations with the same variables to solve the values for both variables.

 

Important Terms Related to Pair of Linear Equations in Two Variables Examples

Polynomial: An algebraic expression with variables having non-negative integers as power and equality on both sides is known as a polynomial.

Degree: The largest value of power given to the variables is known as the degree of the polynomial. A degree 1 polynomial is linear. While degree 2 is quadratic in nature and degree 3 polynomial is cubic. For example, 5x + 7y = 6 is a linear polynomial. Further, we will see how to solve the following pair of linear equations.

 

Representing a Pair of Linear Equations in Two Variables

A pair of linear equations can be represented both algebraically as well as graphically. Let’s look at the equations. The first equation is in the form of a1x + b1y + c1 = 0 and the second equation is given by the form a2x + b2y + c2 = 0 where a1, a2, b1, b2, c1 and c2 are real numbers. Again, a12 + b12 and a22 + b12 are not equal to zero.

Here three important conditions arise:

• If a1/a2 is not equal to b1/b2, then the pair is consistent.

• If a1/a2 is equivalent to b1/b2 but is not similar to c1/c2, then the pair is said to be inconsistent.

• If a1/a2 is equal to b1/b2 and also equal to c1/c2, then the pair is consistent and dependent.

The graphical representation of these equations is also simple. Two lines in a plane can intersect each other, run parallel to each other, or coincide with each other. Consider a pair of linear equations and solve the following pair of linear equations by the elimination method and the substitution method. After this, you will get different values for x and y by putting them in the equations. It can be easily plotted on graph paper.

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Methodology of Solving a Pair of Linear Equations

We can solve these equations graphically, but this is not at all feasible. Graphical methods are the most time consuming and tedious. In cases of non-integral coordinates, plotting it on graph paper becomes very difficult. Hence, we have algebraic ways to solve such problems. The plans include the elimination method, cross multiplication, and method of substitution.

 

Elimination Method

To get an equation in one variable, use the elimination method and either add or subtract the equations. The elimination method of algebraically solving a system of linear equations is the most extensively used method of solving linear equations. When solving linear equations with two or three variables, the elimination method comes in handy. Let’s have a look at how to use the elimination method to solve a system of equations.

• The first step is to multiply or divide both linear equations by a non-zero value to obtain a common coefficient of any of the variables in both equations.

• Add or remove from both equations such that the identical terms are eliminated.

• Simplify the result to produce a final solution of the left-out variable (say, y) in the form of y=c, where c is any constant.

• Finally, use this value to solve either of the supplied equations to discover the value of the other given variable.

 

Cross Multiplication Method

In solving linear equations with two variables, the cross-multiplication method is used. The method of cross-multiplication is the most straightforward way of solving linear equations in two variables. When we have a pair of variables in a linear equation, we use this method. It is the quickest approach for solving a pair of linear equations. We utilise the cross-multiplication approach to solve a pair of linear equations. If a1x+b1y+c1=0 and a2x+b2x+c2=0 are two linear equations, then we can use this approach to obtain the values of x and y.

 

Solved Examples

1. Find out whether the equations given below are Consistent or Inconsistent. 2x + 3y = 5 and 3x – 2y = 9

Ans: a1/a2 = 2/3, b1/b2 = 3/-2 and c1/c2 = 5/9.

Since a1/a2 is not equal to b1/b2, the pair is consistent. These lines intersect each other at some point and have only one single solution.

2. Determine whether the pair of Linear Equations given below has a Unique Solution, an Infinite Number of solutions, or no solution. 3x + y = 10 and 2x + 3y = 7

Ans: a1/a2 = 3/2, b1/b2 = 1/3 and c1/c2 = 10/7.

Since a1/a2 is not equal to b1/b2, the pair is consistent. These lines intersect each other at some point and have only one single solution. Hence, they have a Unique Solution as they cross at an end.