| 2. Method of addition and subtraction
Example Solve y + x = 24 y - x = 4 Solution: y + x = 24 . . . (1) y - x = 4 . . . (2) Adding (1) and (2) y + x = 24 y - x = 4 2 y = 28 y = 14 Inserting y = 14 in (1) 14 + x = 24 x = 10 \ x = 10 and y = 14 is the required solution.
Example Solve x + 2 y = 9; 3 x - 2 y = -5 Solution : x + 2 y = 9 . . . (1) 3 x - 2 y = -5 . . . (2) Observe that coefficient of y in both the equations are opposite number. Hence by adding these two equations, y can be eliminated. x + 2 y = 9 3 x - 2 y = -5 4 x = 4 x = 1 Substituting x = 1 in (1), we get 1 + 2 y = 9 and solving this equation we get y = 4. Therefore, x = 1 and y = 4 is the required solution
|
7.1 Definition |