#41. a) Write the equation in slope-intercept form
b) Give the slope and y-intercept of the line
X=5y-6
Y=
1
6
X+
5
5
#42.Use the slope-intercept form to graph the equation:
!
Y=-2/7X
-1
Plot the y-intercept at (0, -1)
Plot a second point 2 units up and 7 units to the left, at (-7, 1)
The graph looks like this:
#43. Graph the linear equation using the slope and y-intercept
Y=7-2x
Plot the y-intercept at (0, 7)
Plot a second point 2 units to the right and 4 units down, at (2, 3)
The graph looks like this:
#44. The formula y=-0.5x+23 models the percentage of men, y, smoking cigarettes x
years after 1980
Find percentage of men who smoked in 1989
For the year 1989, x = 1989 – 1980 = 9
Then y = -0.5(9) + 23 = 18.5%
#45. Electrical service cost $6 per month plus $.10 per kilowatt-hour of electricity used.
(Assume that a partial kilowatt-hour is not rounded up.)
a) If the resident of an apartment uses 600 kilowatt-hours in 1 month, what is the charge?
The charge is $___
6 + (0.10)(600) = $66
b) Write an equation in slope-intercept form that gives the cost of C of using x kilowatthours in 1 month
C(x) = 0.1x + 6
c) If the monthly electrical bill for the apartment’s residents is $36, how many kilowatthours were used.
36 = 0.1x + 6
30 = 0.1x
x = 300 kilowatt-hours
#46. Find a point-slope equation of the line having the given slope and containing the
given point
M=-7;(8,4)
What is the equation of the line?
In the equation below, type the slope and the coordinates of the point in the appropriate
position.
y-___= ___(x-___)
y – 4 = -7(x – 8)
#47. Find a point-slope form for the equation of the line satisfying the conditions.
Passing through (3,2) and (8,4)
Choose the equation of the line that passes through (3,2) and (8,4)
Select the best answer:
a) y-3=2/5(x-2)
b) y-2=-2/5(x-3)
c) y-2=2/5(x-3)
d) y=8=2/5(x-4)
Slope =
4 "2 2
=
8"3 5
Substituting the point (3, 2) in the point-slope formula gives:
!
(y – 2) = 2/7(x – 3)
#48. Solve the following equation for y
y+3= -4(x-6)
y + 3 = -4x + 24
y = -4x + 27
#49. Write the equation in slope-intercept form
y-2=1/4(x+20)
the equation is y= ___ x + ____
y "2 =
y=
!
1
x +5
4
1
x+7
4
#50. In 1920, the record for a certain race was 45.8 sec. In 1930, it was 45.6 sec.
Let y= the record in the race and x= the number of years since 1920
a) Find the slope-intercept form of a line that fits the data
b) Use the equation in (a) to predict the record in 2003 and in 2006
Find the slope-intercept form of a line that fits the data.
The equation is____
Slope =
45.6 " 45.8 "0.2
=
= "0.02
1930 "1920
10
y = -0.02x + 45.8
!
2003: x = 2003 – 1920 = 83
y = -0.02(83) + 45.8 = 44.14
2006: x = 2006 – 1920 = 86
y = -0.02(86) + 45.8 = 44.08