1. Point-Slope Form
Algebra 1

2. Learning Targets I can interpret an equation in point-slope form
I can write an equation in point-slope form given the correct information

3. Something to think about…
You are given two point: (1, 3) (-4, -12)
For us to write an equation through these points in slope-intercept (y = ax + b) form we need to know the:
slope
y-intercept
We can find the slope but the y-intercept can be difficult.
There is another form of a linear equation that can help!!!!

4. y = ax + b a = slope b = y-intercept y = y1 + a(x – x1) a = slope
Slope-Intercept Form
Point-Slope Form
y = ax + b
a = slope
b = y-intercept
y = y1 + a(x – x1)
a = slope
(x1 , y1) = any given point

5. Try one
You know a line has a slope of 3 and a point on that line is (6, 10), make an equation in point slope form.
y = ___ + ____(x - ____)
y = (x – 6) 10 3 6 y1 a x1

6. Try one
You know a line has a slope of -1/3 and a point on that line is (-9, -4.5), make an equation in point slope form.
y = ___ + ____(x - ____)
y = -4.5 – 1/3(x + 9)
-4.5
-1/3 -9 y1 a x1

7. Try one
You know a line has a slope of 0 and a point on that line is (7, -2), make an equation in point slope form.
y = ___ + ____(x - ____)
y = -2 -2 7 y1 a x1

8. Examples
y = ½x + 4
1. y = 5 + ½ (x – 2) Slope: ½ Point: (2, 5) 2. y = -4 (x – 1) – 2 Slope: -4 Point: (1, -2) 3. y = 2/3 (x + 6) – 8 Slope: 2/3 Point: (-6, 2)
y = -4x + 2
y = 2/3 x – 4

9. Finding Slope You are given two points: (-11, 0) (-7, 2)
Make and equation
Slope = ½
Point = (-11, 0) or (-7, 2)
Y = 0 + ½ (x + 11) or y = 2 + ½ (x + 7)