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Writing Linear Equations
Algebra 2
Section 2-4
Writing in Slope-Intercept Form
Write the equation of the line in slope-intercept
form that passes through pt (0,4) and has a
4
slope
3
Use y  mx  b ONLY when you know slope and
the y-intercept.
Plug in what you know:
Therefore,
4
y  x4
3
4
m  and b  4
3
Point-Slope Form
y  y1  m  x  x1 
 x1 , y1 
is a point and m is the slope.
Useful when you know the slope and a point.
Use when you do not know the y-intercept
Can easily transform between slope-intercept form
and standard form.
Using Point-Slope Form
Write the equation of a line in both slopeintercept and standard form that passes
through the pt (-1,-4) with a slope of -3.
Plug in for
y  y1  m  x  x1 
x1 , y1 , and m
Parallel and Perpendicular Lines

Parallel Lines
◦ Same slope

Perpendicular Lines
◦ Slopes are negative reciprocals
Vertical and Horizontal Lines
Give it a Try!
1. Write an equation in both slope-intercept
and standard form for the line that passes
through (5,-6) and is parallel to the line
2. Write an equation in slope-intercept form
for the line that passes through (3,7) and is
perpendicular to
Give it a Try!
3. Write an equation in both slope-intercept
and standard form for the line that passes
through pt (1/2, -2) and has a slope of -1.
4. Write an equation in both slope-intercept
and standard form for the line that passes
through the points
(-5, 3/2) and (6, 3/2).