20
1. FUNCTIONS AND LINEAR MODELS
Point-slope form of a line
A linear function written as
y
y1 = m(x
x1)
has slope m and passes through the point (x1, y1).
Example. Find the line passing through the points (2, 3) and (5, 7).
Solution
7 3 4
= .
5 2 3
Then use either point with the point-slope form:
4
4
y 3 = (x 2)
y 7 = (x 5)
3
3
4
8
4
20
y 3= x
y 7= x
3
3
3
3
4
1
4
1
y = x+
y = x+
3
3
3
3
4
1
x+y =
standard form
3
3
4x + 3y = 1
better standard form
4x 3y = 1
best standard form
Find the slope: m =
⇤