Download Knowing the slope of a line, m, and the y

Aim #20: How do we graph lines in slope-intercept form?
Homework: Text pg 115 (1-9, 12-13, 16-21), pg 120 (2-20 even #s only)
Do Now: Find the intercepts of the graph below.
10-19-16
y
x
The slope, m, of a line is found by its "rise" in the y-axis divided by its "run" in
the x-axis.
-If a graph is provided, counting "rise over run" is acceptable to determine the
slope. What is the slope of our "do now" graph? ________
-If a graph is not given, to calculate slope, use two points from the equation of
the line and apply the formula below where (x1, y1) and (x2, y2) are the two points:
Calculate the slope of each line that passes through the following points.
1) (9, 4), (-5, 8)
2) (8, -3), (-1, 1)
3) (-10, 8), (6, 8)
4) (4, 7), (5, -3)
Knowing the slope of a line, m, and the y-intercept, b, allows us to
write the equation of a line in slope-intercept form: y = mx + b.
Write the equation of a line in slope-intercept form, y = mx + b,
1) that has a slope of 4 and passes through (0, -8).
a
2) where m = -1 and b = 5.
3) given the graphs on the right:
a)
b
b)
c)
c
4) Is it possible to write the equation of any vertical line in y = mx + b form?
Explain.
Re-write the following equations in slope-intercept form.
5) 3x + y = 8
6) -4y - 4 = 2x
7) 4x + 3y = 12
Graph the equations.
9) y = -3x + 8
10)
11)
12) y = -2
8) 2x + y = 2(x - 1)
Write the equation of a line, in slope-intercept form,
13) that has a slope of 3 and passes through (8, 5).
14) that has a slope of
and passes through (-4, -1).
15) that passes through (9, 4) and (0, -2).
16) that passes through (-3, -2) and (9, -3).
17) Does the graph of the straight line with slope of -2 and y-intercept of -3 pass
through the point (5,-13)?
18) Given the graph of the line represented by the equation y = -3x + b, if b is
decreased by 5 units, the graph of the new line would be shifted 5 units:
(1) right (2) left
(3) up
(4) down
Sum it up!
Vertical lines (whose slope is undefined) are the only lines that cannot be written
in slope-intercept form. Every other line has a slope and a y-intercept.
We can write the equation in the form y = mx + b if we are given:
the slope and y-intercept, the slope and a point or two points.
We can graph lines in the form y = mx + b by starting at the y-intercept and
counting off the slope (rise over run).