CBSE Class 09 Mathematics Revision Notes CHAPTER – 4
LINEAR EQUATIONS IN TWO VARIABLES

1. Linear Equations
2. Solution of a Linear Equation
3. Graph of a Linear Equation in Two Variables
4. Equations of Lines Parallel to x-axis and y-axis

• An equation of the form ax+by+c=0ax+by+c=0 where a, b and c are real numbers such that a and b are not both zero is called a linear equation in two variables.
• A pair of values of x and y which satisfy the equation ax+by+c=0ax+by+c=0 is called a solution of the equation.
• A linear equation in two variables has infinitely many solutions.
• The graph of every linear equation in two variables is a straight line.
• y = 0 is the equation of x-axis and x = 0 is equation of y-axis.
• The graph of x=ax=a is a straight line parallel to the y-axis.
• The graph of y = a is a straight line parallel to the x-axis.
• An equation of the type y = mx represent a line passing through the origin.
• Every point on the graph of a linear equation in two variables is a solution of the equation. Conversely, every solution of the linear equation in two variables represents a point on the graph of the equation.