1.1 SOLUTIONS
dt 1
,2 Chapter One /SOLUTIONS dt dt
CHAPTER ONE dt
d t
1. (a) The story in (a) matches Graph (IV), in which the person forgot her books and had to return home.
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(b) The story in (b) matches Graph (II), the flat tire story. Note the long period of time during which the distance fr
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
om home did not change (the horizontal part).
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(c) The story in (c) matches Graph (III), in which the person started calmly but sped up later.
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The first graph (I) does not match any of the given stories. In this picture, the person keeps going away from hom
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
e, but his speed decreases as time passes. So a story for this might be: I started walking to school at a good pace, but since
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
I stayed up all night studying calculus, I got more and more tired the farther I walked.
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2. The height is going down as time goes on. A possible graph is shown in Figure 1.1. The graph is decreasing.
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
height
time
Figure 1.1 dt
3. The amount of carbon dioxide is going up as time goes on. A possible graph is shown in Figure 1.2. The graph is increasing.
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
CO2
time
Figure 1.2 dt
, 1.1 SOLUTIONS
dt 3
4. The number of air conditioning units sold is going up as temperature goes up. A possible graph is shown in Figure 1.
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
3. The graph is increasing.
dt dt dt dt
AC units
dt
temperature
Figure 1.3 dt
5. The noise level is going down as distance goes up. A possible graph is shown in Figure 1.4. The graph is decreasing.
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
noise leveldt
distance
Figure 1.4 dt
6. If we let t represent the number of years since 1900, then the population increased between t = 0 and t = 40, stay
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ed approximately constant between t = 40 and t = 50, and decreased for t ≥ 50. Figure 1.5 shows one possible graph. M
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
any other answers are also possible.
dt dt dt dt dt
population
years
20 d t d t 40 d t d t 60 d t d t 80 d t 100 120 since 1900
d t dt
dt
Figure 1.5 dt
, 4 Chapter One /SOLUTIONS dt dt
7. Amount of grass G = f (r) increases as the amount of rainfall r increases, so f (r) is an increasing function.
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
8. We are given information about how atmospheric pressure P = f (ℎ) behaves when the altitude ℎ decreases: as altitude
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
ℎ decreases the atmospheric pressure P increases. This means that as altitude ℎ increases the atmospheric pressure P
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
decreases. Therefore, P = f (ℎ) is a decreasing function.
d t dt dt d t dt d
t dt dt dt dt
9. We are given information about how battery capacity C = f (T ) behaves when air temperature T decreases: as T decrease
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
s, battery capacity C also decreases. This means that increasing temperature T increases battery capacity C. Theref
dt dt dt dt dt dt dt dt dt dt dt d t dt dt dt dt
ore, C = f (T ) is an increasing function.
d t d t dt d
t dt dt dt dt dt
10. Time T = f (m) increases as m increases, so f (m) is increasing.
dt d t dt dt dt dt dt dt dt dt dt dt dt
11. The attendance A = f (P ) decreases as the price P increases, so f (P ) is a decreasing function.
dt dt dt dt d
t dt dt dt dt dt dt dt dt dt d
t dt dt dt dt dt
12. The cost of manufacturing C = f (v) increases as the number of vehicles manufactured v increases, so f (v) is an increasin
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
g function.
dt
13. We are given information about how commuting time, T = f (c) behaves as the number of cars on the road c decrease
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
s: as c decreases, commuting time T also decreases. This means that increasing the number of cars on the road c increa
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
ses commuting time T . Therefore, T = f (c) is an increasing function.
dt dt dt dt dt dt d t dt d
t dt dt dt dt
14. The statement f (4) = 20 tells us that W = 20 when t = 4. In other words, in 2019, Argentina produced 20 million metri
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
c tons of wheat.
dt dt dt
15. (a) If we consider the equation
d t dt dt dt dt
C = 4T − 160
d t dt d t dt
simply as a mathematical relationship between two variables C and T , any T value is possible. However, if we thin
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
k of it as a relationship between cricket chirps and temperature, then C cannot be less than 0. Since C = 0 lea
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt d t dt dt
ds to 0 = 4T − 160, and so T = 40 F, we see that T cannot be less than 40 F. In addition, we are told that the
dt d t dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt d
function is not defined for temperatures above 134 . Thus, for the function C = f (T ) we have
t dt dt dt dt dt dt dt d t dt dt dt dt dt dt dt d
t dt dt dt
Domain = All T values between 40 F and 134 F dt dt dt dt dt dt dt dt dt d t
= All T values with 40 ≤ T ≤ 134
dt dt d t dt dt dt dt d t dt
= [40, 134].
dt dt
(b) Again, if we consider C = 4T − 160 simply as a mathematical relationship, its range is all real C values. However
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
, when thinking of the meaning of C = f (T ) for crickets, we see that the function predicts cricket chirps per mi
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
nute between 0 (at T = 40 F) and 376 (at T = 134 F). Hence,
dt dt dt dt d t dt dt dt dt dt dt d t dt dt dt
Range = All C values from 0 to 376 dt dt dt dt dt dt dt dt
= All C values with 0 ≤ C ≤ 376
dt dt dt dt dt dt dt dt dt
= [0, 376].
dt dt
16. (a) The statement f (19) = 415 means that C = 415 when t = 19. In other words, in the year 2019, the concentration
dt dt dt d
t dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
of carbon dioxide in the atmosphere was 415 ppm.
dt dt dt dt dt dt dt dt
(b) The expression f (22) represents the concentration of carbon dioxide in the year 2022.
dt dt dt dt dt dt dt dt dt dt dt dt dt
17. (a) At p = 0, we see r = 8. At p = 3, we see r = 7.
d t dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
(b) When p = 2, we see r = 10. Thus, f (2) = 10. dt dt dt dt dt dt dt dt dt dt d
t dt dt
18. Substituting x = 5 into f (x) = 2x + 3 gives dt dt dt dt d t dt dt dt dt dt dt
f (5) = 2(5) + 3 = 10 + 3 = 13.
d
t dt dt dt dt dt dt dt dt dt dt
19. Substituting x = 5 into f (x) = 10x − x2 gives dt dt dt dt d t dt dt dt dt dt dt
f (5) = 10(5) − (5)2 = 50 − 25 = 25.
d
t dt dt dt dt dt dt dt dt dt dt
20. We want the y-coordinate of the graph at the point where its x-coordinate is 5. Looking at the graph, we see that the
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
y-coordinate of this point is 3. Thus dt dt dt dt dt dt
f (5) = 3. d
t dt dt
dt 1
,2 Chapter One /SOLUTIONS dt dt
CHAPTER ONE dt
d t
1. (a) The story in (a) matches Graph (IV), in which the person forgot her books and had to return home.
d t dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
(b) The story in (b) matches Graph (II), the flat tire story. Note the long period of time during which the distance fr
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
om home did not change (the horizontal part).
dt dt dt dt dt dt dt
(c) The story in (c) matches Graph (III), in which the person started calmly but sped up later.
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
The first graph (I) does not match any of the given stories. In this picture, the person keeps going away from hom
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
e, but his speed decreases as time passes. So a story for this might be: I started walking to school at a good pace, but since
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
I stayed up all night studying calculus, I got more and more tired the farther I walked.
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
2. The height is going down as time goes on. A possible graph is shown in Figure 1.1. The graph is decreasing.
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
height
time
Figure 1.1 dt
3. The amount of carbon dioxide is going up as time goes on. A possible graph is shown in Figure 1.2. The graph is increasing.
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
CO2
time
Figure 1.2 dt
, 1.1 SOLUTIONS
dt 3
4. The number of air conditioning units sold is going up as temperature goes up. A possible graph is shown in Figure 1.
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
3. The graph is increasing.
dt dt dt dt
AC units
dt
temperature
Figure 1.3 dt
5. The noise level is going down as distance goes up. A possible graph is shown in Figure 1.4. The graph is decreasing.
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
noise leveldt
distance
Figure 1.4 dt
6. If we let t represent the number of years since 1900, then the population increased between t = 0 and t = 40, stay
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
ed approximately constant between t = 40 and t = 50, and decreased for t ≥ 50. Figure 1.5 shows one possible graph. M
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
any other answers are also possible.
dt dt dt dt dt
population
years
20 d t d t 40 d t d t 60 d t d t 80 d t 100 120 since 1900
d t dt
dt
Figure 1.5 dt
, 4 Chapter One /SOLUTIONS dt dt
7. Amount of grass G = f (r) increases as the amount of rainfall r increases, so f (r) is an increasing function.
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
8. We are given information about how atmospheric pressure P = f (ℎ) behaves when the altitude ℎ decreases: as altitude
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
ℎ decreases the atmospheric pressure P increases. This means that as altitude ℎ increases the atmospheric pressure P
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
decreases. Therefore, P = f (ℎ) is a decreasing function.
d t dt dt d t dt d
t dt dt dt dt
9. We are given information about how battery capacity C = f (T ) behaves when air temperature T decreases: as T decrease
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
s, battery capacity C also decreases. This means that increasing temperature T increases battery capacity C. Theref
dt dt dt dt dt dt dt dt dt dt dt d t dt dt dt dt
ore, C = f (T ) is an increasing function.
d t d t dt d
t dt dt dt dt dt
10. Time T = f (m) increases as m increases, so f (m) is increasing.
dt d t dt dt dt dt dt dt dt dt dt dt dt
11. The attendance A = f (P ) decreases as the price P increases, so f (P ) is a decreasing function.
dt dt dt dt d
t dt dt dt dt dt dt dt dt dt d
t dt dt dt dt dt
12. The cost of manufacturing C = f (v) increases as the number of vehicles manufactured v increases, so f (v) is an increasin
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
g function.
dt
13. We are given information about how commuting time, T = f (c) behaves as the number of cars on the road c decrease
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
s: as c decreases, commuting time T also decreases. This means that increasing the number of cars on the road c increa
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
ses commuting time T . Therefore, T = f (c) is an increasing function.
dt dt dt dt dt dt d t dt d
t dt dt dt dt
14. The statement f (4) = 20 tells us that W = 20 when t = 4. In other words, in 2019, Argentina produced 20 million metri
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
c tons of wheat.
dt dt dt
15. (a) If we consider the equation
d t dt dt dt dt
C = 4T − 160
d t dt d t dt
simply as a mathematical relationship between two variables C and T , any T value is possible. However, if we thin
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
k of it as a relationship between cricket chirps and temperature, then C cannot be less than 0. Since C = 0 lea
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt d t dt dt
ds to 0 = 4T − 160, and so T = 40 F, we see that T cannot be less than 40 F. In addition, we are told that the
dt d t dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt d
function is not defined for temperatures above 134 . Thus, for the function C = f (T ) we have
t dt dt dt dt dt dt dt d t dt dt dt dt dt dt dt d
t dt dt dt
Domain = All T values between 40 F and 134 F dt dt dt dt dt dt dt dt dt d t
= All T values with 40 ≤ T ≤ 134
dt dt d t dt dt dt dt d t dt
= [40, 134].
dt dt
(b) Again, if we consider C = 4T − 160 simply as a mathematical relationship, its range is all real C values. However
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
, when thinking of the meaning of C = f (T ) for crickets, we see that the function predicts cricket chirps per mi
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
nute between 0 (at T = 40 F) and 376 (at T = 134 F). Hence,
dt dt dt dt d t dt dt dt dt dt dt d t dt dt dt
Range = All C values from 0 to 376 dt dt dt dt dt dt dt dt
= All C values with 0 ≤ C ≤ 376
dt dt dt dt dt dt dt dt dt
= [0, 376].
dt dt
16. (a) The statement f (19) = 415 means that C = 415 when t = 19. In other words, in the year 2019, the concentration
dt dt dt d
t dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
of carbon dioxide in the atmosphere was 415 ppm.
dt dt dt dt dt dt dt dt
(b) The expression f (22) represents the concentration of carbon dioxide in the year 2022.
dt dt dt dt dt dt dt dt dt dt dt dt dt
17. (a) At p = 0, we see r = 8. At p = 3, we see r = 7.
d t dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
(b) When p = 2, we see r = 10. Thus, f (2) = 10. dt dt dt dt dt dt dt dt dt dt d
t dt dt
18. Substituting x = 5 into f (x) = 2x + 3 gives dt dt dt dt d t dt dt dt dt dt dt
f (5) = 2(5) + 3 = 10 + 3 = 13.
d
t dt dt dt dt dt dt dt dt dt dt
19. Substituting x = 5 into f (x) = 10x − x2 gives dt dt dt dt d t dt dt dt dt dt dt
f (5) = 10(5) − (5)2 = 50 − 25 = 25.
d
t dt dt dt dt dt dt dt dt dt dt
20. We want the y-coordinate of the graph at the point where its x-coordinate is 5. Looking at the graph, we see that the
dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt dt
y-coordinate of this point is 3. Thus dt dt dt dt dt dt
f (5) = 3. d
t dt dt