Mathematics
Use graph paper for this question. Take 2 cm = 1 unit on both the axes.
(i) Draw the graphs of x + y + 3 = 0 and 3x - 2y + 4 = 0. Plot only three points per line.
(ii) Write down the co-ordinates of the point of intersection of the lines.
(iii) Measure and record the distance of the point of intersection of the lines from the origin in cm.
Graphical Solution
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Answer
(i)
First equation: x + y + 3 = 0
Step 1:
Give three suitable values to the variable x and find the corresponding values of y.
Let x = 0, then 0 + y + 3 = 0 ⇒ y = -3
Let x = -4, then -4 + y + 3 = 0 ⇒ y = 1
Let x = -6, then -6 + y + 3 = 0 ⇒ y = 3
Step 2:
Make a table (as given below) for the different pairs of the values of x and y:
| x | 0 | -4 | -6 |
|---|---|---|---|
| y | -3 | 1 | 3 |
Step 3:
Plot the points, from the table, on a graph paper and then draw a straight line passing through the points plotted on the graph.
Second equation: 3x - 2y + 4 = 0
Step 1:
Give three suitable values to the variable x and find the corresponding values of y.
Let x = 0, then 3 0 - 2y + 4 = 0 ⇒ y = 2
Let x = 2, then 3 2 - 2y + 4 = 0 ⇒ y = 5
Let x = 4, then 3 4 - 2y + 4 = 0 ⇒ y = 8
Step 2:
Make a table (as given below) for the different pairs of the values of x and y:
| x | 0 | 2 | 4 |
|---|---|---|---|
| y | 2 | 5 | 8 |
Step 3:
Plot the points, from the table, on a graph paper and then draw a straight line passing through the points plotted on the graph.

(ii) Both the straight line drawn meet at the point A. As it is clear from the graph, co-ordinates of the common point A are (-2, -1).
Hence, co-ordinates of the point of intersection of the lines are (-2, -1).
(iii) In triangle OAB,
Using pythagoras theorem,
OA2 = AB2 + OB2
= 22 + 12
= 4 + 1
= 5
OA =
OA = 2.2 cm
Hence, the distance of the point of intersection of the lines from the origin is 2.2 cm.
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