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Complex Numbers and Quadratic Equations MCQs

Class 11 Maths — questions with answers and worked explanations.

20 free questions Class 11 Maths Answers + explanations No sign-up

These questions are drawn from the Pariksha Sutra question bank for Complex Numbers and Quadratic Equations, part of the Class 11 Maths syllabus. Each one shows the correct answer and, where a method helps, the working behind it.

Read the question, decide your answer before looking, then check the explanation — that is what turns practice into marks. If a question catches you out, the explanation is the part worth re-reading.

Questions

Question 1
The value of i^2 is:
  1. i
  2. -i
  3. 1
  4. -1
Answer: -1
Question 2
The sum i + i^2 + i^3 + i^4 equals:
  1. i
  2. 1
  3. -1
  4. 0
Answer: 0
Question 3
For complex numbers z1 and z2, |z1 z2| equals:
  1. |z1| - |z2|
  2. |z1|/|z2|
  3. |z1| |z2|
  4. |z1| + |z2|
Answer: |z1| |z2|
Question 4
The argument (principal) of the complex number i is:
  1. -pi/2
  2. pi/2
  3. pi
  4. 0
Answer: pi/2
Question 5
The quotient (1 + i)/(1 - i) equals:
  1. -1
  2. 1
  3. i
  4. -i
Answer: i
Question 6
The conjugate of i is:
  1. -i
  2. 1
  3. i
  4. -1
Answer: -i
Question 7
The modulus r in the polar form of z = 1 + i is:
  1. 1/sqrt(2)
  2. 1
  3. sqrt(2)
  4. 2
Answer: sqrt(2)
Question 8
The roots of x^2 + 4 = 0 are:
  1. 2i and -2i
  2. i and -i
  3. 4i and -4i
  4. 2 and -2
Answer: 2i and -2i
Question 9
The value of i^7 is:
  1. -i
  2. 1
  3. i
  4. -1
Answer: -i
Question 10
If z1 = 3 + 4i and z2 = 1 - 2i, then z1 - z2 equals:
  1. 4 + 6i
  2. 4 + 2i
  3. 2 - 6i
  4. 2 + 6i
Answer: 2 + 6i
Question 11
The modulus of the purely real number -7 is:
  1. 7
  2. 0
  3. 49
  4. -7
Answer: 7
Question 12
The argument (principal) of the complex number -1 is:
  1. 0
  2. pi/2
  3. -pi
  4. pi
Answer: pi
Question 13
If z = (2 + 3i) + (4 - i), then z equals:
  1. 2 + 4i
  2. 6 - 2i
  3. 6 + 2i
  4. -2 + 2i
Answer: 6 + 2i
Question 14
The imaginary part of (3 + i)(1 + i) is:
  1. 2
  2. 3
  3. 1
  4. 4
Answer: 4
Question 15
If conjugate(z) = z, then z is:
  1. purely real
  2. undefined
  3. purely imaginary
  4. zero
Answer: purely real
Question 16
The argument (principal) of the complex number 1 + i is:
  1. pi/3
  2. pi/4
  3. pi/2
  4. pi/6
Answer: pi/4
Question 17
The product (2 + 3i)(2 - 3i) equals:
  1. 13
  2. 4 - 9i
  3. 5
  4. -5
Answer: 13
Question 18
Expressed in a + ib form, 1/(2 - 3i) equals:
  1. (2 - 3i)/13
  2. (3 + 2i)/13
  3. (2 + 3i)/13
  4. (2 + 3i)/5
Answer: (2 + 3i)/13
Question 19
The sum of a complex number z and its conjugate equals:
  1. |z|^2
  2. 2 Re(z)
  3. 2 Im(z)
  4. 2i Im(z)
Answer: 2 Re(z)
Question 20
The complex number represented by the point (-2, -3) in the Argand plane is:
  1. 2 - 3i
  2. -3 - 2i
  3. -2 + 3i
  4. -2 - 3i
Answer: -2 - 3i

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