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
Linear equations in two variables class 9 Examples