Recall that the
slope- intercept form of a linear equation is y = mx + b where m is the
slope and b is the y - coordinate of the y -intercept
Recall that the point-slope of a linear equation is
where m is the slope
and 
is a given point on the line
Don’t forget that the slope measures the change in the y -coordinate relative
to the
change in the x-coordinate, or, more precisely,
Model Problems:
1. What are the slope and the y-intercept of the fol lowing linear equation?
Answer: m = 3 and y-int = (0,4.5)
2. Find the slope of the line which passes through the points (5,100) and
(8,67).
Answer: 
3. Find the equation of the line which passes through the points (5,100) and
(8,67).
Using the above result, we know that m = −11
| y −100 = −11(x − 5) |
Here we’re using the point-slope form |
| |
|
| y −100 = −11x + 55 |
Distribute −11 |
| |
|
| y = −11x +155 |
Solve for y |
4. Find an equation of the line graphed on the right :
Practice Exercises:
1. Which of the following equations is most likely
re presented by the given graph?
2. Which of the following graphs most likely represents
the equation y = −2.1x + 50?
3. Which of the following graphs most likely represents
the equation y = 3.11x −10?
Given a pair of points below, find the slope of the line
which passes through them.
4. (5, 2) and (-1, 1)
5. (12, -4) and (10, 10)
6. (1, 4) and (-10, 4)
Find the equation of the line which passes through the given points.
7. (3, -5) and (8, 5)
8. (10, 3) and (15, -17)
9. (1.2, 4) and (2.2, 5)
Find the slope and the y-intercept of the lines whose equations are given below.
10. 2y − 2 = 6x
11. 10y + 3 = −20x − 20
12. 110x +1 = 100y −1
Answers:
1. (c)
2. (a)
3. (b)
4.
5. − 7
6. 0
7. y = 2x −11
8. y = −4x + 43
9. y = x + 2.8
10. slope = 3, y int = (0,1)
11. slope = −2, y int = (0,−2.3)
12. slope = 1.1, y int = (0,0.02)
