Mr. Sims
slope-intercept form
y = mx + b
slope
rise
run
Algebra 2
Section 9.4
Slope-Intercept Method
of Drawing Graphs
y-intercept
{where the line crosses
the y-axis}
1
y  x 3
2
1
slope =
2
y-intercept = 3
to graph:
start at y-intercept and put a point
(from there) - use the slope to get another point
½ means go “up 1 and right 2”
Mr. Sims
y = 2x + 5
slope = 2
y-intercept = 5
to graph:
start at y-intercept and put a point
(from there) – use slope to get another point
slope = 2 = 2 go up 2 and right 1
1
1
y   x 1
3
1
slope = 
3
y-intercept = 1
to graph:
start at y-intercept and put a point
(from there) – use slope to get another point
slope = -1 go down 1 and right 3
3
Mr. Sims
y = 4x - 3
slope = 4
y-intercept = -3
y = -x – 2
slope = -1
y-intercept = -2
Mr. Sims
3x + 2y = 4
-3x
-3x
2y = -3x + 4
get in slope-intercept form
3
y x2
2
3
slope = 
2
y-intercept = 2
3y = 15
y = 5 get in slope-intercept form
slope = 0 {horizontal line}
y-intercept = 5
Mr. Sims
Write the equation of the line
in slope-intercept form.
y-intercept = 2
slope = 3
y = 3x + 2
y-intercept = -9
9
slope =
8
9
y  x 9
8
Mr. Sims
y-intercept = -7
2
slope = 
3
2
y   x 7
3
x = -3
Mr. Sims
Determine whether a point having the given coordinates is on the
line described by the given equation.
(x,y)
(1,2) , 3x + 2y = 7 substitute coordinates into equation
-if both sides are equal, then yes the point lies on the line
3(1) + 2(2) = 7
3+4=7
7=7
yes, the point lies on the line
(-3,-2) , 3x – 2y = -6
3(-3) – 2(-2) = -6
-9 + 4 = -6
-5 -6
no, the point does not lie on the line
Mr. Sims
(-1,-2) , -2x + y + 4 = 0
-2(-1) + (-2) + 4 = 0
2–2+4=0
4 0
no, the point does not lie on the line
y = 2x – 4
y-int. = - 4
slope = 2
point: (-1,-2)
Mr. Sims
Algebra 2
Section 9.4
Assignment
Draw the graph of each equation.
2
1.) y   x  2
3
1
2.) y   x  4
2
3.) y = -2x + 1
4.) y = 5x + 3
5.) y = -3x – 1
6.) y = -x + 5
7.) x – 3y – 9 = 0
8.) 3x – 4y = 12
9.) x = 4
10.) 2x + 5y + 15 = 0
Mr. Sims
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Mr. Sims