1. Y X
Equation of Lines

2. At the end of this lesson you will be able to:X
Write equations of straight lines.
Calculate the slope and y – intercept of a line passing through two points.

3. Intercepts of a line
Y-intercept (b): The y-coordinate of the point where the graph of a line crosses the y-axis.
(0,b)
(a,0)
X-intercept (a): The x-coordinate of the point where the graph of a line crosses the x-axis.

4. Equation of a line
An equation of a line is a general rule followed by every point lying on that line.
Consider a line l given in this graph.
The points (-2, 0), (-1, 1), (0, 2), (1, 3), (2, 4) etc. are some points on the line l. l
y-coordinate of each of these points is 2 more than the x-coordinate.
In general, if (x, y) is any point on the line, then we may say that,
y = x + 2
This is considered as an equation of the line l.

5. Slope – Intercept form of a line
Consider a line with y-intercept ‘b’ and slope ‘m’.
(0,b)
Let (x, y) be any point on the line
(x,y)
Then , The equation of the line is ,

6. Example 1
Find the equation of the line whose slope is 𝟐 𝟑 and y-intercept 3.
Solution:
Y-axis
X-axis
(0,3)

7. Example 2
Find the equation of the line passing through the points (0,2) and (5,2)
Solution:
Y-axis
X-axis
(0,2)
(5,2)

8. Horizontal And Vertical Lines
Y-axis
X-axis
(a,b)
(a,0)

9. General Equation Of a Line

10. Example 3
Solution:
Y-axis
X-axis
(3,7)
(0,3)

11. Example 4
Solution:

12. Practice Question