2.4 Writing Equations of Lines
Equations of Lines
SlopeSlope-Intercept Form
y = mx + b
use if given slope and yintercept
PointPoint-Slope Form
y − y 1 = m(x − x 1 )
use if given slope and a point
Standard Form
Ax + By = C
Recall: slope =
***NOTE:
**NOTE: If given two points, first find the slope using m =
−A
B
y2 − y1
, then use the
x2 − x1
Point-Slope Formula with only one of the two given points.
Ex:
Ex: Write the equation of the line with the following characteristics:
a) point (−3, 4)
2
slope =
3
b) (0, 4)
c) passes through point (4, −1)
and parallel to y = −x + 4
d) passes through (2, −3) and
perpendicular to y = 2x – 3
e) point (4, 8) and (1, 2)
slope = −
1
2
Writing Equations of Lines Given the Graph
• Find the slope of the line.
• Plug one point and slope into y = mx + b to solve for y-intercept.
• Write final equation.
Ex:
Ex Write the equation of each line shown. State your answer in Slope−Intercept Form.
f)
g)
h)
i)