Question
Solve the following simultaneous equation graphically.
x + y = 0; 2x – y = 9
x + y = 0; 2x – y = 9
✓
Answer
The given simultaneous equations are
$x+y=0$
$\therefore \quad y=-x$
$2 x-y=9$
$\therefore \quad y=2 x-9$
The two lines intersect at point (3, -3).
∴ x = 3 and y = -3 is the solution of the simultaneous equations x + y = 0 and 2x – y = 9.
$x+y=0$
$\therefore \quad y=-x$
| x | 0 | 2 | -2 | -1 |
| y | 0 | -2 | 2 | 1 |
| (x, y) | (0, 0) | (2, -2) | (-2, 2) | (-1, 1) |
$2 x-y=9$
$\therefore \quad y=2 x-9$
| x | 0 | 2 | 5 | 4 |
| y | -9 | -5 | 1 | -1 |
| (x, y) | (0, -9) | (2, -5) | (5, 1) | (4, -1) |
The two lines intersect at point (3, -3).
∴ x = 3 and y = -3 is the solution of the simultaneous equations x + y = 0 and 2x – y = 9.
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