Complex Numbers
Q. Find the real part of the complex number 4 + 5i. (2023)
Solution
The real part of the complex number 4 + 5i is 4.
Correct Answer: A — 4
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Q. If z = -2 + 2i, what is the value of |z|? (2019)
Solution
|z| = √((-2)^2 + (2)^2) = √(4 + 4) = √8 = 2√2.
Correct Answer: A — 2√2
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Q. If z = 1 + i, what is the value of z^2? (2022)
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A.
2i
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B.
1 + 2i
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C.
2
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D.
0
Solution
z^2 = (1 + i)^2 = 1^2 + 2(1)(i) + i^2 = 1 + 2i - 1 = 2i.
Correct Answer: B — 1 + 2i
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Q. If z = 1 + i, what is the value of z²? (2022)
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A.
0
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B.
2i
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C.
2
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D.
1 + 2i
Solution
z² = (1 + i)² = 1² + 2(1)(i) + i² = 1 + 2i - 1 = 2i.
Correct Answer: D — 1 + 2i
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Q. If z = 2 + 2i, what is |z|^2? (2021)
Solution
|z|^2 = (2^2 + 2^2) = 4 + 4 = 8.
Correct Answer: A — 8
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Q. If z = 2 - 3i, what is the conjugate of z? (2020)
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A.
2 + 3i
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B.
2 - 3i
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C.
-2 + 3i
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D.
-2 - 3i
Solution
The conjugate of z = 2 - 3i is 2 + 3i.
Correct Answer: A — 2 + 3i
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Q. If z = 3 + 4i, what is the imaginary part of z? (2022) 2022
Solution
The imaginary part of the complex number z = 3 + 4i is 4.
Correct Answer: B — 4
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Q. If z = 3 + 4i, what is the value of z + z* (where z* is the conjugate of z)? (2017)
Solution
z + z* = (3 + 4i) + (3 - 4i) = 6.
Correct Answer: B — 8
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Q. If z = 3 + 4i, what is the value of z + z̅? (2022)
Solution
z + z̅ = (3 + 4i) + (3 - 4i) = 6.
Correct Answer: B — 8
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Q. If z = 4 + 3i, what is the real part of z? (2023)
Solution
The real part of the complex number z = 4 + 3i is 4.
Correct Answer: A — 4
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Q. If z = 5 + 12i, what is the argument of z? (2022)
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A.
arctan(12/5)
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B.
arctan(5/12)
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C.
π/2
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D.
0
Solution
The argument of z = 5 + 12i is given by arctan(12/5).
Correct Answer: A — arctan(12/5)
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Q. What is the argument of the complex number -1 + 0i? (2021)
Solution
The argument of -1 + 0i is π (180 degrees) since it lies on the negative x-axis.
Correct Answer: A — π
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Q. What is the modulus of the complex number 3 + 4i? (2023)
Solution
The modulus is calculated as √(3^2 + 4^2) = √(9 + 16) = √25 = 5.
Correct Answer: A — 5
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Q. What is the product of the complex numbers (1 + i) and (1 - i)? (2023) 2023
Solution
(1 + i)(1 - i) = 1^2 - i^2 = 1 - (-1) = 2.
Correct Answer: A — 2
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Q. What is the product of the complex numbers 2 + 3i and 4 - i? (2021)
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A.
11 + 10i
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B.
14 + 5i
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C.
5 + 10i
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D.
10 + 5i
Solution
(2 + 3i)(4 - i) = 8 - 2i + 12i - 3i^2 = 8 + 10i + 3 = 11 + 10i.
Correct Answer: A — 11 + 10i
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Q. What is the real part of the complex number 4 + 5i? (2023)
Solution
The real part of the complex number 4 + 5i is 4.
Correct Answer: A — 4
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Q. What is the real part of the complex number 7 - 4i? (2023)
Solution
The real part of the complex number 7 - 4i is 7.
Correct Answer: A — 7
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Q. What is the square of the modulus of the complex number 1 + 2i? (2014)
Solution
The modulus is √(1^2 + 2^2) = √(1 + 4) = √5. The square of the modulus is 5.
Correct Answer: A — 5
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Q. What is the square of the modulus of the complex number 1 + i? (2020)
Solution
The modulus is √(1^2 + 1^2) = √2, and the square of the modulus is 2.
Correct Answer: A — 2
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Q. What is the sum of the complex numbers 3 + 2i and 1 - 4i? (2023)
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A.
4 - 2i
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B.
2 - 2i
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C.
4 + 2i
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D.
2 + 2i
Solution
(3 + 2i) + (1 - 4i) = (3 + 1) + (2 - 4)i = 4 - 2i.
Correct Answer: A — 4 - 2i
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Q. What is the value of (1 + i)(1 - i)? (2019)
Solution
(1 + i)(1 - i) = 1^2 - i^2 = 1 - (-1) = 1 + 1 = 2.
Correct Answer: A — 2
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Q. What is the value of (2 + 3i) / (1 + i)? (2015)
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A.
1 + 2i
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B.
2 - i
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C.
3 + 2i
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D.
1 - 2i
Solution
Multiply numerator and denominator by the conjugate of the denominator: (2 + 3i)(1 - i) / (1 + i)(1 - i) = (2 - 2i + 3i + 3) / (1 + 1) = (5 + i) / 2 = 2.5 + 0.5i.
Correct Answer: B — 2 - i
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Q. What is the value of (2 + 3i)(2 - 3i)? (2019)
Solution
Using the difference of squares: (a + b)(a - b) = a² - b². Here, (2)² - (3i)² = 4 - (-9) = 4 + 9 = 13.
Correct Answer: A — 13
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Q. What is the value of (3 + 4i) / (1 + i)? (2021)
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A.
2 + i
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B.
1 + 2i
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C.
3 - 4i
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D.
1 - i
Solution
Multiplying numerator and denominator by the conjugate of the denominator: (3 + 4i)(1 - i) / (1 + i)(1 - i) = (3 - 3i + 4i + 4) / 2 = (7 + i) / 2 = 2 + i.
Correct Answer: A — 2 + i
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Q. Which of the following is the conjugate of the complex number 2 - 3i? (2020)
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A.
2 + 3i
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B.
2 - 3i
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C.
3 - 2i
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D.
3 + 2i
Solution
The conjugate of a complex number a + bi is a - bi. Thus, the conjugate of 2 - 3i is 2 + 3i.
Correct Answer: A — 2 + 3i
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Q. Which of the following is the conjugate of the complex number 5 - 3i? (2020)
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A.
5 + 3i
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B.
5 - 3i
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C.
-5 + 3i
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D.
-5 - 3i
Solution
The conjugate of a complex number a + bi is a - bi. Thus, the conjugate of 5 - 3i is 5 + 3i.
Correct Answer: A — 5 + 3i
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