These comprehensive RBSE Class 9 Maths Notes Chapter 4 Linear Equations will give a brief overview of all the concepts.

## RBSE Class 9 Maths Chapter 4 Notes Linear Equations in Two Variables

1. The equation in which there are two variables of degree one is called linear equation ‘ in two variables. Any equation which can be put in the form ax + by + c = 0, where a, b and c are real numbers, and a and b are not both zero, is called a linear equation in two variables.

2. Solution of a linear equation : Let ax + by + c = 0, where a, b, c are real numbers such that a ≠ 0 and b ≠ 0. Then, any pair of values of x and y which satisfies the equation ax + by + c = 0, is called a solution of it, i.e., when the values are substituted in place of variables in the equation, the two sides (left hand side and right hand side) must be equal.

3. A linear equation in two variables has infinitely many solutions.

4. The graph of a linear equation in two variables is always a straight line.

5. x = 0 is the equation of the y-axis and y = 0 is the equation of the x-axis.

6. The graph of x = a is a straight line parallel to the y-axis.

7. The graph of y = a is a straight line parallel to the x-axis.

8. An equation of the type y = mx represents a line passing through the origin.

9. An equation of the type y = mx + c represents a line which does not pass through the origin.

10. Simultaneous equations is the pair of two linear equations in two variables. The values of both variables that satisfy both equations are the solutions of the simultaneous equations.

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