Linear equations in two variables class 9 – The equation that can be represented in the form of px + qy + r = 0 is called a two variable linear equation. [where p, q & r are real, and p & q are not 0]. For example: 2.5p + 3q = 9, x + 8y = 9, 9u – 15v = 19, etc. There are infinitely many solutions possible for a linear equation in 2 variables. The graph of such equations is always a straight line. In a two variable linear equation, x = 0 denotes the equation of y axis and y = 0 denotes the equation of the x-axis. The graph of equation x = c represents a straight line parallel to the y-axis. Similarly, the graph of equation y = c represents a straight line parallel to the x axis. The equation y = cx (where, c = constant) represents a line passing through the center (origin). All the points on the graph of a 2 variable linear equation is a solution of the linear equation. The graph of a linear equation represents the solution of a linear equation. The solution remains unaffected when:

**(i) **Same quantity is either subtracted or added from both the sides (LHS and RHS) of the equation.

**(ii)** If both LHS and RHS of equation are multiplied or divided by the same non-zero

number.

### Linear equations in two variables class 9 Examples