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Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 1
8.1 Exponential Properties Involving Products
Answers
1. a. base is a
b. exponent is 5
c. the power is the exponent (5)telling us how many times to multiply “a”
d. written as: 𝑎 ∙ 𝑎 ∙ 𝑎 ∙ 𝑎 ∙ 𝑎
2. negative
3. positive
4. negative
5. Order of operations must be applied. In the first expression you are squaring 5 first
then applying the –sign, resulting in an answer of −(5 ∙ 5) = −25. In the second
expression because the (-5) is in brackets you keep the –sign with the 5 when you
multiply it: (−5 ∙ −5) = 25.
6. 22
7. (−3)3
8. 𝑦5
9. (3𝑎)4
10. 45
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 2
11. 3𝑥3
12. (−2𝑎)4
13. 63𝑥2𝑦4
14. 1
15. 0
16. 343
17. −36
18. 625
19. 177147
20. 128
21. 4096
22. 64
23. 0.00001
24. −0.216
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 3
25. 10077696
26. 4096
27. 576
28. 𝑥6
29. 𝑥9
30. 𝑦15
31. 6𝑦5
32. 60𝑎7
33. 𝑎12
34. 𝑥2𝑦2
35. 81𝑎8𝑏12
36. −32𝑥5𝑦20𝑧10
37. 12𝑥3𝑦5
38. 8𝑥3𝑦5𝑧5
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 4
39. 4𝑎6𝑏6
40. −12800𝑥5
41. 64𝑎14
42. 1728𝑥3𝑦3
43. 6𝑥7𝑦6
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 5
8.2 Exponential Properties Involving Quotients
Answers
1. 625
2. 1296
3. 729
4. 0.003251536859
5. 𝑎
6. 𝑥4
7. 𝑥5
8. 𝑎5
9. 𝑎2𝑏2
10. 64
11. 625
12. 10.4976
13. 𝑎3𝑏9
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 6
14. 𝑥4 𝑦2
15. 3𝑥𝑦
16. 𝑏4
16𝑎8
17. 𝑥6
18. 64𝑎2
𝑏13
19. 3𝑎
20. 3𝑥4
21. 2.0736𝑎24
22. 5𝑥4
4𝑦
23. 𝑥6
𝑦6
24. 3.75𝑎3
𝑏7
25. . 44̅𝑎3𝑏10
26. 3𝑎2𝑐4
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 7
8.3 Negative Exponents
Answers
1. 𝑦2
𝑥
2. 1
𝑥4
3. 𝑥4
4. 1
𝑥
5. 2
𝑥2
6. 𝑥2
𝑦3
7. 3
𝑥𝑦
8. 3
𝑥3
9. 𝑎2
𝑏3𝑐
10. 4𝑦3
𝑥
11. 2𝑦3
𝑥2
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 8
12. 𝑏2
𝑎2
13. 27𝑏6𝑐9
𝑎6
14. 1
15. 𝑎8
16. 5𝑥−2𝑦
17. 64𝑎−2𝑏13
18. −27
19. 1
20. 64
21. 24
22. 9
23. 121
144
24. 512
25. 4092
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 9
26. 41
27. 36
54 or 729
625
28. 9324
29. 367
9
30. 4
35
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 10
8.4 Fractional Exponents
Answers
1. √𝑎23
2. 𝑎2
3. √𝑥23
𝑦
4. 𝑧7
𝑥3𝑦5
5. 𝑥√𝑥
√𝑦3
6. 27𝑥3𝑦−1
7. 2𝑎−3𝑏2
8. 1
108𝑥5𝑦−5 𝑜𝑟 .00925926𝑥5𝑦−5
9. 𝑎2 𝑏−10
10. 𝑥−5𝑦4
11. 3𝑥𝑦
12. 3𝑥7𝑦−2
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 11
13. 𝑎−2𝑏−3𝑐
14. 𝑥−1𝑦
15. ±64
16. 1
17. 49
18. 8
27 𝑜𝑟 .2962963
19. 1
27𝑜𝑟 .03703704
20. 4
21. 1
2 𝑜𝑟 .5
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 12
8.5 Scientific Notation
Answers
1. 310.2
2. 74000
3. 0.00175
4. 0.000029
5. 0.000000000999
6. 1.2 𝑥 105
7. 1.765244 𝑥 106
8. 6.3 𝑥 10
9. 9.654 𝑥 103
10. 6.53937 𝑥 108
11. 1.000000006 𝑥 109
12. 1.2 𝑥 10
13. 2.81 𝑥 10−3
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 13
14. 2.7 𝑥 10−8
15. 3 𝑥 10−3
16. 5.6 𝑥 10−5
17. 5.007 𝑥 10−5
18. 9.54 𝑥 10−12
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 14
8.6 Scientific Notation with a Calculator
Answers
1. 2.784 × 1018
2. 1.976 × 10−22
3. 4.59 × 10−5
4. 3.68 × 10−6
5. 1.37 × 1015
6. . 629̅̅ ̅̅ ̅̅ × 1017
7. 1.1045 × 10−23
8. 7.35315 × 105
9. 4.17 × 107
10. 3.47 × 10−11
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 15
8.7 Exponential Growth
Answers
1. The general equation for an exponential equation is 𝑦 = 𝑎(𝑏)𝑥, where 𝑎 is the starting
value, 𝑏 is the growth factor, 𝑥 is the number of times the growth factor has been
applied and 𝑦 is the solution.
2. In a linear equation we often find a variable with an exponent, while in an exponential
growth equation the variable is always the exponent.
3. The growth factor of an exponential equation must always be greater than 1.
4. False, the form of the equation is correct, but 𝑏 must be greater than 1.
5. The 𝑦 − 𝑖𝑛𝑡𝑒𝑟𝑐𝑒𝑝𝑡 (when 𝑥 = 0) in any exponential growth function will always be
equal to 𝑎 or the starting value, (regardless of what 𝑏 is, when it is raised to the 𝑥
power and 𝑥 = 0 then 𝑏𝑥 = 1 and 𝑎 times 1 is always 𝑎)
6.
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 16
7.
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 17
8.
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 18
9.
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 19
10.
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 20
11.
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 21
12.
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 22
13.
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 23
14. 𝑦 = 𝑎(𝑏)𝑥
𝑎 = 10 𝑝𝑒𝑜𝑝𝑙𝑒
𝑏 = 10 𝑝𝑒𝑜𝑝𝑙𝑒
𝑐 = 6 𝑤𝑒𝑒𝑘𝑠
If everyone maintains the chain then 10 million people will receive the letter the
sixth week.
15. 𝑦 = 𝑎(𝑏)𝑥
𝑎 = $200.00
𝑏 = 100% + 7.5% = 1.075
𝑐 = 21 − 10 = 11 𝑦𝑒𝑎𝑟𝑠
By her 21st birthday Nadia will have approximately $443.12 in her account.
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 24
8.8 Exponential Decay
Answers
1. Exponential decay is when a function decreases from its original value regularly
according to the noted decay factor.
2. “𝑏” in an exponential decay function must always be a fraction between 0 and 1.
3. If 𝑓(𝑥) = 𝑎(𝑏)𝑥 then 𝑓(0) is always equal to a. (𝑏0 will always equal 1 and 𝑎 × 1 is 𝑎)
This means that the 𝑦 − 𝑖𝑛𝑡𝑒𝑟𝑐𝑒𝑝𝑡 of an exponential function is always equal to 𝑎 or
the starting value.
4.
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 25
5.
6.
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 26
7.
8. a) Growth factor is .70.
b) Initial value is 1.
c) 𝑉(65) = 8.54 × 10−11
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 27
9. a.
b. 𝑦 = 𝑎(𝑏)𝑥 The initial value is 2,000,000 and the growth factor is ¾ or .75, with 𝑥
= time in days so: 𝑦 = 2,000,000(. 75)𝑥
c. 10 days after ≈112,627
d. 14 days after ≈ 35.636
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 28
8.9 Geometric Sequences and Exponential Functions
Answers
1. A geometric sequence is a sequence of numbers in which each number in the sequence
is found by multiplying the previous number by a fixed amount called the common
ratio.
2. a. 𝑎4 = 1 × 23 = 8
b. 𝑎10 = 1 × 29 = 512
c. 𝑎25 = 1 × 224 = 16777216
d. 𝑎60 = 1 × 259 = 576460752303000000 ≈ 5.76 × 1017
3. Yes, If we divide any number by the number preceding it we always get the same
answer: -1. Therefore it is a sequence found by multiplying the previous number by a
common ratio and therefore a geometric sequence.
4. After 3 days, the population will be 81 million.
5. 6 ÷ 8 = .75, 𝑟 = 0.754
6. 4 ÷ 2 = 2, 𝑟 = 2
7. 3 ÷ 9 =1
3, 𝑟 =
1
3
8. −8 ÷ 2 = −4, 𝑟 = −4
9. 2, 6, 18, 54, 162
10. 90, −30, 10, −10
3,
10
9
11. 6, −12, 24, −48, 96
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 29
12. 192 ÷ 48 = 4, 𝑟 = 4, 𝑇ℎ𝑒𝑟𝑒𝑓𝑜𝑟𝑒: 3, 12, 48, 192, 768
13. 𝑊ℎ𝑒𝑛 𝑟 =1
3, 𝑡ℎ𝑒𝑛: 81, 27, 9, 3, 1 𝑊ℎ𝑒𝑛 𝑟 = −
1
3 𝑡ℎ𝑒𝑛: 81, −27, 9, −3, 1
14. 𝑟 =2
3, 𝑡ℎ𝑒𝑟𝑒𝑓𝑜𝑟𝑒:
9
4,
3
2, 1,
2
3,
4
9
15. 𝑎6 = 4 × 25 = 128
16. 𝑎4 = −7 ×3
4
3 = 2.953125
17. 𝑎10 = −10 × −39 = 196830
18.
a. 𝑦 =. 8𝑥
b. 𝑦 =. 85 = 0.328 𝑓𝑒𝑒𝑡
19.
a. 37 = 2187 blocks
b. The 6th stack is 243 blocks tall
20.
a. The ball will bounce 11.25 feet high after the third bounce.
b. The ball will bounce 0.2005 feet high after the seventeenth bounce.
21.
a. The rope will stretch 43.2 feet on the third bounce.
b. The rope will stretch 0.4354 feet on the twelfth bounce.
22.
a. After 5 hrs, or ten doublings, the population will be 30,720
b. After 12 doublings, or 6hrs, the population will be apx 123,000
Chapter 8 – Exponents and Exponential Functions Answer Key
CK-12 Basic Algebra Concepts 30
8.10 Applications of Exponential Functions
Answers
1. After six hours there will be approximately 80.8% left.
2. In the year 2020 there will be approximately 1147 bird species left.
3. In the year 2007 there would be approximately 370 stores in Nadia’s chain.
4. In 12 years there will be approximately $833.82 in the account.
5. Approximately 120,481
6. About 3840 bacteria
7. Approximately $13.44, 5 years from now.
8. a.
b. 𝑦 = 7200 ∗ 0.82𝑥
c. $989.63
9. a. 𝑦 = 10,112,620 ∗ 0.995𝑥
b. 9,715,124
c. About 4.25 years (early in 2008)
d. 10,317,426