Math II ยท N-CN.1

Understanding `i` and Representing Complex Numbers as `a + bi`

Complex numbers let students solve equations and model rotations, waves, signals, and systems that real numbers alone cannot describe cleanly.

Concept Number and Quantity
Domain The Complex Number System
Read time 1 minutes

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Problem Library

Problems in the App From This Objective

144 problems across 12 archetypes in the app.

use cycle `i, -1, -i, 1`.
12 problems Warmup Practice Mixed Review Assessment
Problem 1

Simplify i^5.

Problem 2

Simplify i^18.

Problem 3

Simplify i^27.

Problem 4

Simplify i^44.

Open in simulator
Problem 5

Simplify i^101.

Problem 6

Simplify i^0.

Problem 7

Simplify i^1.

Problem 8

Simplify i^2.

Problem 9

Simplify i^3.

Problem 10

Simplify i^4.

Problem 11

Simplify i^6.

Problem 12

Simplify i^10.

factor `sqrt(-1)`.
12 problems Warmup Practice Mixed Review Assessment
Problem 13

Rewrite sqrt(-25) using i.

Problem 14

Rewrite sqrt(-12) using i.

Problem 15

Rewrite sqrt(-7) using i.

Problem 16

Rewrite sqrt(-72) using i.

Problem 17

Rewrite sqrt(-4) using i.

Problem 18

Rewrite sqrt(-81) using i.

Open in simulator
Problem 19

Rewrite sqrt(-8) using i.

Problem 20

Rewrite sqrt(-18) using i.

Problem 21

Rewrite sqrt(-20) using i.

Problem 22

Rewrite sqrt(-3) using i.

Problem 23

Rewrite sqrt(-11) using i.

Problem 24

Rewrite sqrt(-50) using i.

parse `a+bi`.
12 problems Warmup Practice Mixed Review Assessment
Problem 25

Identify the real and imaginary parts of complex number 4+7i.

Problem 26

Identify the real and imaginary parts of complex number -3-2i.

Problem 27

Identify the real and imaginary parts of complex number 9.

Problem 28

Identify the real and imaginary parts of complex number -5i.

Problem 29

Identify the real and imaginary parts of complex number 2+3i.

Problem 30

Identify the real and imaginary parts of complex number -1+6i.

Problem 31

Identify the real and imaginary parts of complex number 8-4i.

Problem 32

Identify the real and imaginary parts of complex number -7-i.

Problem 33

Identify the real and imaginary parts of complex number 12.

Problem 34

Identify the real and imaginary parts of complex number 10i.

Problem 35

Identify the real and imaginary parts of complex number -i.

Problem 36

Identify the real and imaginary parts of complex number 1+i.

Open in simulator
order real part plus imaginary part.
12 problems Warmup Practice Mixed Review Assessment
Problem 37

Write expression 3i+5 in standard complex form.

Problem 38

Write expression sqrt(-16)+2 in standard complex form.

Problem 39

Write expression 7-i^2+4i in standard complex form.

Problem 40

Write expression -2i+sqrt(-9)-1 in standard complex form.

Problem 41

Write expression i^3+6 in standard complex form.

Problem 42

Write expression sqrt(-25)-3i+1 in standard complex form.

Open in simulator
Problem 43

Write expression 4-i^4+2i in standard complex form.

Problem 44

Write expression 5i-sqrt(-49)+10 in standard complex form.

Problem 45

Write expression 2i^2+3i-5 in standard complex form.

Problem 46

Write expression 1/i+7 in standard complex form.

Problem 47

Write expression sqrt(-1)+sqrt(-100)-2 in standard complex form.

Problem 48

Write expression -i^5+3i-4 in standard complex form.

understand subset relationships.
12 problems Warmup Practice Mixed Review Assessment
Problem 49

Classify number 7 as real, imaginary, or complex.

Problem 50

Classify number -4i as real, imaginary, or complex.

Problem 51

Classify number 3+2i as real, imaginary, or complex.

Problem 52

Classify number 0 as real, imaginary, or complex.

Problem 53

Classify number sqrt(-9) as real, imaginary, or complex.

Problem 54

Classify number 1.5 as real, imaginary, or complex.

Problem 55

Classify number i as real, imaginary, or complex.

Problem 56

Classify number -5+i as real, imaginary, or complex.

Open in simulator
Problem 57

Classify number -10 as real, imaginary, or complex.

Problem 58

Classify number 0.5i as real, imaginary, or complex.

Problem 59

Classify number -2-3i as real, imaginary, or complex.

Problem 60

Classify number sqrt(16) as real, imaginary, or complex.

plot real part horizontally and imaginary part vertically.
12 problems Warmup Practice Mixed Review Assessment
Problem 61

Represent complex number 3+4i on the complex plane.

Problem 62

Represent complex number -2+5i on the complex plane.

Problem 63

Represent complex number 6- i on the complex plane.

Problem 64

Represent complex number -4i on the complex plane.

Problem 65

Represent complex number 7 on the complex plane.

Problem 66

Represent complex number -5-2i on the complex plane.

Problem 67

Represent complex number 1-3i on the complex plane.

Problem 68

Represent complex number 8i on the complex plane.

Problem 69

Represent complex number -10 on the complex plane.

Problem 70

Represent complex number 0.5+2.5i on the complex plane.

Open in simulator
Problem 71

Represent complex number 100+200i on the complex plane.

Problem 72

Represent complex number -0.1-0.2i on the complex plane.

connect definition to equation solving.
12 problems Warmup Practice Mixed Review Assessment
Problem 73

Use i to solve equation x^2=-1.

Open in simulator
Problem 74

Use i to solve equation x^2=-9.

Problem 75

Use i to solve equation x^2+16=0.

Problem 76

Use i to solve equation x^2=-5.

Problem 77

Use i to solve equation x^2=-25.

Problem 78

Use i to solve equation x^2=-7.

Problem 79

Use i to solve equation x^2+49=0.

Problem 80

Use i to solve equation x^2+11=0.

Problem 81

Use i to solve equation 2x^2=-8.

Problem 82

Use i to solve equation 5x^2=-30.

Problem 83

Use i to solve equation x^2+100=0.

Problem 84

Use i to solve equation x^2+8=0.

simplify using `i^2=-1`.
12 problems Warmup Practice Mixed Review Assessment
Problem 85

Evaluate expression 3+2i-5i using i^2=-1.

Problem 86

Evaluate expression 4i^2+7 using i^2=-1.

Problem 87

Evaluate expression 2(3+i)-5i using i^2=-1.

Problem 88

Evaluate expression -6i+2i^2+1 using i^2=-1.

Problem 89

Evaluate expression -3i^2+5 using i^2=-1.

Problem 90

Evaluate expression 2(1-i^2)+3i using i^2=-1.

Problem 91

Evaluate expression 5i-i^2+2i-1 using i^2=-1.

Problem 92

Evaluate expression (7+i^2)-(3-2i) using i^2=-1.

Problem 93

Evaluate expression -4(2i^2+i)+10 using i^2=-1.

Problem 94

Evaluate expression i^2+2i^2+3i+4 using i^2=-1.

Problem 95

Evaluate expression (6+4i^2)/2 using i^2=-1.

Problem 96

Evaluate expression 10-3i+i^2-5 using i^2=-1.

Open in simulator
compare real and imaginary parts.
12 problems Warmup Practice Mixed Review Assessment
Problem 97

Determine whether complex expressions 3+2i+i and 3+3i are equal.

Problem 98

Determine whether complex expressions 5+i^2 and 4 are equal.

Problem 99

Determine whether complex expressions 2-3i and -3i+2 are equal.

Problem 100

Determine whether complex expressions 4+2i and 2+4i are equal.

Problem 101

Determine whether complex expressions (2+3i) + (1-i) and 3+2i are equal.

Problem 102

Determine whether complex expressions (5-2i) - (1+i) and 4+3i are equal.

Problem 103

Determine whether complex expressions (1+i)*(1-i) and 2 are equal.

Problem 104

Determine whether complex expressions (2+i)*(1+i) and 1-3i are equal.

Problem 105

Determine whether complex expressions i^3 and -i are equal.

Problem 106

Determine whether complex expressions i^4 and -1 are equal.

Problem 107

Determine whether complex expressions 1/(1+i) and 0.5 - 0.5i are equal.

Problem 108

Determine whether complex expressions 2i * i + 3 and 1+i are equal.

Open in simulator
reason that real squares are nonnegative.
12 problems Warmup Practice Mixed Review Assessment
Problem 109

Explain why sqrt(-4) requires complex numbers.

Problem 110

Explain why sqrt(-11) requires complex numbers.

Problem 111

Explain why sqrt(-1) requires complex numbers.

Problem 112

Explain why sqrt(-9) requires complex numbers.

Problem 113

Explain why sqrt(-25) requires complex numbers.

Problem 114

Explain why sqrt(-2) requires complex numbers.

Problem 115

Explain why sqrt(-16) requires complex numbers.

Open in simulator
Problem 116

Explain why sqrt(-100) requires complex numbers.

Problem 117

Explain why sqrt(-5) requires complex numbers.

Problem 118

Explain why sqrt(-49) requires complex numbers.

Problem 119

Explain why sqrt(-3) requires complex numbers.

Problem 120

Explain why sqrt(-1/4) requires complex numbers.

read coordinates as real and imaginary parts.
12 problems Warmup Practice Mixed Review Assessment
Problem 121

Convert complex-plane point 3, 4 to standard complex form.

Problem 122

Convert complex-plane point -2, 5 to standard complex form.

Problem 123

Convert complex-plane point 0, -6 to standard complex form.

Problem 124

Convert complex-plane point 7, 0 to standard complex form.

Problem 125

Convert complex-plane point 1/2, -3/4 to standard complex form.

Problem 126

Convert complex-plane point -5, -8 to standard complex form.

Problem 127

Convert complex-plane point 6, -1 to standard complex form.

Problem 128

Convert complex-plane point -9, 2 to standard complex form.

Problem 129

Convert complex-plane point 0, 10 to standard complex form.

Problem 130

Convert complex-plane point -11, 0 to standard complex form.

Open in simulator
Problem 131

Convert complex-plane point 2/3, 1/5 to standard complex form.

Problem 132

Convert complex-plane point -3/2, 1 to standard complex form.

catch power-of-i, standard-form, and real/imaginary-part mistakes.
12 problems Warmup Practice Mixed Review Assessment
Problem 133

Correct the complex-number representation error in i^6 is simplified as i.

Problem 134

Correct the complex-number representation error in sqrt(-36) is simplified as -6.

Problem 135

Correct the complex-number representation error in For 4-7i, the imaginary part is 7.

Problem 136

Correct the complex-number representation error in Point (2,-3) is written as -3+2i.

Problem 137

Correct the complex-number representation error in i^3 is simplified as 1.

Problem 138

Correct the complex-number representation error in i^10 is simplified as i.

Problem 139

Correct the complex-number representation error in sqrt(-4) is simplified as -2i.

Problem 140

Correct the complex-number representation error in sqrt(-9) is simplified as 3.

Problem 141

Correct the complex-number representation error in For 5+2i, the real part is 2.

Problem 142

Correct the complex-number representation error in For 1-i, the imaginary part is i.

Problem 143

Correct the complex-number representation error in Point (-1,5) is written as 5-i.

Open in simulator
Problem 144

Correct the complex-number representation error in Point (3,0) is written as 3i.