This document discusses solving linear equations graphically. It provides examples of plotting points for linear equations in the form of y=mx+c and solving systems of linear equations by finding the point of intersection between two lines graphed on the same coordinate plane. Specific examples include solving the systems x+y=7 and x-y=3, finding the solution set is (5,2) by plotting the lines and identifying their intersection point. It also discusses cases where lines are parallel and have no solution or where multiple lines intersect at the same point, representing the solution set.

1. PEDAGOGY OF
MATHEMATICS – PART II
BY
Dr. I. UMA MAHESWARI
Principal
Peniel Rural College of Education,Vemparali,
Dindigul District
iuma_maheswari@yahoo.co.in

2. STD IX
CHAPTER 3 – ALGEBRA
Ex – 3.10

24. (i) y = 2x
Solution:
When x = -2, y = 2 (-2) = -
4
When x = 0, y = 2 (0) = 0
When x = 2, y = 2 (2) = 4
When x = 3, y = 2 (3) = 6

25. Plot the points (-2, -4) (0, 0) (2, 4) and
(3, 6) in the graph sheet we get a
straight line.

26. (ii) y = 4x – 1
Solution:
When x = – 1; y = 4 (-1) -1 ⇒ y = -5
When x = 0; y = 4 (0) – 1 = 0 – 1 ⇒ y
= -1
When x = 2; y = 4 (2) -1 = 8 – 1 ⇒ y
= l
Plot the points (-1, -5) (0, -1) and (2, 7) in the graph sheet we get a straight line.
At the time of printing change the direction.

28. Plot the points (-2, 0) (0, 3)
and (2, 6) in the graph sheet
we get a straight line.

29. Plot the points (-2, 10) (0, 7)
and (2, 4) in the graph sheet
we get a straight line.

30. Solve graphically (i) x + y = 7, x – y
= 3
Solution:
x + y = 7
y = 7 – x
Plot the points (-2, 9), (0, 7) and (3, 4) in the
graph sheet
x – y = 3
-y = -x + 3
y = x – 3

31. Plot the points (-2, -5), (0, -3) and (4, 1) in the same graph sheet.
The point of intersection is (5, 2)
of lines (1) and (2).
The solution set is (5,2).

32. Plot the points (-2, 5), (0, 2) and (2, -1) the same
graph sheet
Here both the equations are identical, but in different
form.
Their solution is same.
This equations have an infinite number of solution.

34. The given two lines are parallel.
∴They do not intersect a point.
∴There is no solution.

36. The two lines l1 and l2 intersect at (-3, -3). The
solution set is (-3, -3).

38. The two lines l1 and l2 intersect at (1, 3).
∴The solution set is (1, 3).

40. The two lines l1 and l2 intersect at (-3, 3)
∴The solution set is (-3, 3)

42. Plot the points (30, 70), (50, 50), (60, 40) and
(70,30) in the graph sheet
x – y = 50
-y = -x + 50
y = x – 50

43. Plot the points (40, -10), (50, 0), (60, 10) and (70, 20) in the
same graph sheet
The two cars intersect at (75, 25)
The speed of the first car 75 km/hr
The speed of the second car 25 km/hr