Algebra I
Name:
SOL A.6b Writing Linear Equations
Block:
Date:
Point-Slope Form
Essential Quet
Essential Question(s): What do you need to write an equation in point-slope form?
Point-Slope Form
When an equation is in point-slope form,
you can read the ____- and ____- coordinates of a point on the line
and the _____________ of the line.
Example: Write an equation in point-slope form
Write an equation in point-slope form of the line that passes through the
point (4, –3) and has a slope of 2.
Write point-slope form:
Substitute slope (m)
and the coordinates (x1, y1) :
Practice:
Write an equation in point-slope form of the line with the given information.
1) Passes through (–1, 4), slope = 2
2) slope = –2, passes through (6, –7)
Example: Graph an equation in point-slope form
We can also graph an equation in point-slope form.
Identify the slope & a point on the line and use that information to graph the line.
Graph the equation y + 2 =
2
(x – 3).
3
point-slope form:
Step 1: Identify the slope & the point.
slope = ______
point: ________
Step 2: Plot the point.
Step 3: Use slope to find a second point on the line (remember slope =
Then, draw a line through both points.
Practice
3
(x + 1)
4
1) Graph the equation
y–1=
2) Graph the equation
y + 3 = –2(x – 2)
rise
)
run
Example: Write an equation in point-slope form from a graph
Write an equation in point-slope form of the line shown.
Step 1: Find the slope of the line.
.
.
Step 2: Write the equation in point-slope form. You can use either given point.
Use (–1, 3)
Use (1, 1)
Point-slope form:
Point-slope form:
Substitute m, x1 & y1
Substitute m, x1 & y1
.
Example: Write an equation in point-slope form from two points
Write an equation of the line in point-slope form that passes through
the points (–2, 5) and (4, –1).
Step 1: Find the slope of the line using the slope formula.
Step 2: Write the equation in point-slope form. You can use either given point.
Practice:
1) Write an equation of the line in point-slope form that passes through
the points (5, 6) and (3, 7).
2) Write an equation of the line in point-slope form that passes through
the points (–4, –7) and (–2, 7).
Summary: