# Class 11 Maths MCQ – Complex Numbers and Quadratic Equations

This set of Class 11 Maths Chapter 5 Multiple Choice Questions & Answers (MCQs) focuses on “Complex Numbers and Quadratic Equations”. These MCQs are created based on the latest CBSE syllabus and the NCERT curriculum, offering valuable assistance for exam preparation.

1. Value of i(iota) is ____________
a) -1
b) 1
c) (-1)1/2
d) (-1)1/4

Explanation: Iota is used to denote complex number.
The value of i (iota) is $$\sqrt{-1}$$ i.e. (-1)1/2.

2. Is i(iota) a root of 1+x2=0?
a) True
b) False

Explanation: 1+x2 = 0
1 + i2 = 1 – 1 = 0.
So, it is a root of 1 + x2 = 0.

3. In z=4+i, what is the real part?
a) 4
b) i
c) 1
d) 4+i

Explanation: In z=a+bi, a is real part and b is imaginary part.
So, in 4+i, real part is 4.

4. In z=4+i, what is imaginary part?
a) 4
b) i
c) 1
d) 4+i

Explanation: In z=a+bi, a is real part and b is imaginary part.
So, in 4+i, imaginary part is 1.

5. (x+3) + i(y-2) = 5+i2, find the values of x and y.
a) x=8 and y=4
b) x=2 and y=4
c) x=2 and y=0
d) x=8 and y=0

Explanation: If two complex numbers are equal, then corresponding parts are equal i.e. real parts of both are equal and imaginary parts of both are equal.
x+3 = 5 and y-2 = 2
x = 5-3 and y = 2+2
x=2 and y=4.

6. If z1 = 2+3i and z2 = 5+2i, then find sum of two complex numbers.
a) 4+8i
b) 3-i
c) 7+5i
d) 7-5i

Explanation: In addition of two complex numbers, corresponding parts of two complex numbers are added i.e. real parts of both are added and imaginary parts of both are added.
So, sum = (2+5) + (3+2) i = 7+5i.

7. 0+0i is ______________________for complex number z.
b) additive identity element
c) multiplicative identity element
d) multiplicative inverse

Explanation: On adding zero (0+0i) to a complex number, we get same complex number so 0+0i is additive identity element for complex number z i.e. z+0 = z.

8. 1+0i is _________________ for complex number z.
b) additive identity element
c) multiplicative identity element
d) multiplicative inverse

Explanation: On multiplying one (1+0i) to a complex number, we get same complex number so 1+0i is multiplicative identity element for complex number z i.e. z*1=z.

9. -z is _________________ for complex number z.
b) additive identity element
c) multiplicative identity element
d) multiplicative inverse

Explanation: On adding negative of complex number (-z) to complex number z, we get additive identity element zero i.e. z+(-z)=0.

10. 1/z is _________________ for complex number z.
b) additive identity element
c) multiplicative identity element
d) multiplicative inverse

Explanation: On multiplying reciprocal of complex number (1/z) to complex number z, we get multiplying inverse one i.e. z*1=z.

11. If z1 = 2+3i and z2 = 5+2i, then find z1-z2.
a) -3+1i
b) 3-i
c) 7+5i
d) 7-5i

Explanation: In subtracting one complex number from other, difference of corresponding parts of two complex numbers is calculated. So, z1-z2 = (2-5) + (3-2) i = -3+1i.

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