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NCERT Solutions for Miscellaneous Exercise Chapter 4 Class 11 - Complex Numbers and Quadratic Equations

NCERT Solutions for Miscellaneous Exercise Chapter 4 Class 11 - Complex Numbers and Quadratic Equations

Edited By Komal Miglani | Updated on May 05, 2025 04:30 PM IST

Complex numbers are generally considered to be abstract and difficult to understand at first, but they play a significant role in various domains such as signal processing, quantum physics and computer graphics. Similarly, quadratic equations are widely used in the fields of architecture, finance and astronomy to predict the outcomes and design the solutions.

The Miscellaneous Exercise of Class 11 Maths Chapter 4 provided in the NCERT discusses the key concepts provided in the chapter Complex Numbers and Quadratic Equations. This exercise consists of questions ranging from topics such as fundamentals of complex numbers, algebraic operations, and conjugates of complex numbers etc. Understanding the concepts given in complex numbers and quadratic equations builds a strong foundation for more advanced topics in mathematics, such as higher algebra, calculus, and even complex analysis. The NCERT solutions provided here are a useful exercise to get conceptual clarity on the topic of complex numbers and quadratic equations.

This Story also Contains
  1. Class 11 Maths Chapter 1 Complex Numbers and Quadratic Equations Miscellaneous Exercise Solutions - Download PDF
  2. NCERT Solutions Class 11 Maths Chapter 4: Miscellaneous Exercise
  3. Topics covered in Chapter 4 Complex Numbers and Quadratic Equations Miscellaneous Exercise
  4. NCERT Solutions of Class 11 Subject Wise
  5. Subject-Wise NCERT Exemplar Solutions

Class 11 Maths Chapter 1 Complex Numbers and Quadratic Equations Miscellaneous Exercise Solutions - Download PDF

Download PDF



NCERT Solutions Class 11 Maths Chapter 4: Miscellaneous Exercise

Question 1: Evaluate [i18+(1i)25]3 .

Answer:

The given problem is
[i18+(1i)25]3
Now, we will reduce it into
[i18+(1i)25]3=[(i4)4i2+1(i4)6i]3
=[14.(1)+116.i]3 (i4=1,i2=1)
=[1+1i]3
=[1+1i×ii]3
=[1+ii2]3
=[1+i1]3=[1i]3
Now,
(1+i)3=(13+i3+3.12.i+3.1.i2) (using (a+b)3=a3+b3+3.a2.b+3.a.b2)
=(1i+3i+3(1)) (i3=i,i2=1)
=(1i+3i3)=(2+2i)
=22i
Therefore, answer is 22i

Question 2: For any two complex numbers z1 and z2 , prove that Re(z1z2)=Rez1Rez2Imz1Imz2

Answer:

Let two complex numbers are
z1=x1+iy1
z2=x2+iy2
Now,
z1.z2=(x1+iy1).(x2+iy2)
=x1x2+ix1y2+iy1x2+i2y1y2
=x1x2+ix1y2+iy1x2y1y2 (i2=1)
=x1x2y1y2+i(x1y2+y1x2)
Re(z1z2)=x1x2y1y2
=Re(z1z2)Im(z1z2)

Hence proved

Question 3: Reduce (114i21+i)(34i5+i) to the standard form.

Answer:

Given problem is
(114i21+i)(34i5+i)
Now, we will reduce it into

(114i21+i)(34i5+i)=((1+i)2(14i)(1+i)(14i))(34i5+i)
=(1+i2+8i14i+i4i2)(34i5+i)
=(1+9i13i4(1))(34i5+i)
=(1+9i53i)(34i5+i)
=(3+4i+27i36i225+5i15i3i2)=(3+31i+362510i+3)=33+31i2810i=33+31i2(145i)

Now, multiply numerator an denominator by (14+5i)
33+31i2(145i)×14+5i14+5i
462+165i+434i+155i22(142(5i)2) (using (ab)(a+b)=a2b2)
462+599i1552(19625i2)
307+599i2(196+25)=307+599i2×221=307+599i442=307442+i599442

Therefore, answer is 307442+i599442

Question 4: If xiy=aibcid , prove that (x2+y2)2=a2+b2c2+d2.

Answer:

the given problem is

xiy=aibcid
Now, multiply the numerator and denominator by

c+id
xiy=aibcid×c+idc+id
=(ac+bd)+i(adbc)c2i2d2=(ac+bd)+i(adbc)c2+d2
Now, square both the sides
(xiy)2=((ac+bd)+i(adbc)c2+d2)2
=(ac+bd)+i(adbc)c2+d2
x2y22ixy=(ac+bd)+i(adbc)c2+d2
On comparing the real and imaginary part, we obtain

x2y2=ac+bdc2+d2  and  2xy=adbcc2+d2   (i)

Now,
(x2+y2)2=(x2y2)2+4x2y2
=(ac+bdc2+d2)2+(adbcc2+d2)2    (using (i))
=a2c2+b2d2+2acbd+a2d2+b2c22adbc(c2+d2)2
=a2c2+b2d2+a2d2+b2c2(c2+d2)2
=a2(c2+d2)+b2(c2+d2)(c2+d2)2
=(a2+b2)(c2+d2)(c2+d2)2
=(a2+b2)(c2+d2)

Hence proved.

Question 5: If z1=2i,z2=1+i , find |z1+z2+1z1z2+1| .

Answer:

It is given that
z1=2i,z2=1+i
Then,
|z1+z2+1z1z2+1|=|2i+1+i+12i1i+1|=|42(1i)|=|2(1i)|
Now, multiply the numerator and denominator by 1+i
|2(1i)×1+i1+i|=|2(1+i)12i2|=|2(1+i)1+1|=|1+i|
Now,
|1+i|=12+12=1+1=2
Therefore, the value of

|z1+z2+1z1z2+1| is 2

Question 6: If a+ib=(x+i)22x2+1 , prove that a2+b2=(x2+1)2(2x2+1)2 .

Answer:

It is given that
a+ib=(x+i)22x2+1
Now, we will reduce it into

a+ib=(x+i)22x2+1=x2+i2+2xi2x2+1=x21+2xi2x2+1=x212x2+1+i2x2x2+1
On comparing real and imaginary part. we will get
a=x212x2+1 and b=2x2x2+1
Now,
a2+b2=(x212x2+1)2+(2x2x2+1)2
=x4+12x2+4x2(2x2+1)2
=x4+1+2x2(2x2+1)2
=(x2+1)2(2x2+1)2
Hence proved

Question 7: (i) Let z1=2i,z2=2+i. Find

Re(z1z2z1¯)

Answer:

It is given that
z1=2i and z2=2+i
Now,
z1z2=(2i)(2+i)=4+2i+2ii2=4+4i+1=3+4i
And
z¯1=2+i
Now,
z1z2z¯1=3+4i2+i=3+4i2+i×2i2i=6+3i+8i4i222i2=6+11i+44+1 =2+11i5=25+i115
Now,
Re(z1z2z1)=25
Therefore, the answer is

25

Question 7:(ii) Let z1=2i,z2=2+i. Find

Im(1z1z1¯)

Answer:

It is given that
z1=2i
Therefore,
z¯1=2+i
NOw,
z1z¯1=(2i)(2+i)=22i2=4+1=5 (using (ab)(a+b)=a2b2)
Now,
1z1z¯1=15
Therefore,
Im(1z1z¯1)=0
Therefore, the answer is 0.

Question 8: Find the real numbers x andy if (xiy)(3+5i) is the conjugate of 624i .

Answer:

Let
z=(xiy)(3+5i)=3x+5xi3yi5yi2=3x+5y+i(5x3y)
Therefore,
z¯=(3x+5y)i(5x3y)               (i)
Now, it is given that
z¯=624i                    (ii)
Compare (i) and (ii) we will get
(3x+5y)i(5x3y)=624i
On comparing real and imaginary part. we will get
3x+5y=6   and   5x3y=24
On solving these we will get
x=3   and   y=3

Therefore, the value of x and y are 3 and -3 respectively

Question 9: Find the modulus of 1+i1i1i1+i .

Answer:

Let
z=1+i1i1i1+i
Now, we will reduce it into
z=1+i1i1i1+i=(1+i)2(1i)2(1+i)(1i)=12+i2+2i12i2+2i12i2 =4i1+1=4i2=2i
Now,
rcosθ=0  and  rsinθ=2
square and add both the sides. we will get,
r2cos2θ+r2sin2θ=02+22
r2(cos2θ+sin2θ)=4
r2=4                  (cos2θ+sin2θ=1)
r=2                  (r>0)

Therefore, modulus of

1+i1i1i1+i is 2

Question 10: If (x+iy)3=u+iv , then show that ux+vy=4(x2y2).

Answer:

it is given that
(x+iy)3=u+iv
Now, expand the Left-hand side
x3+(iy)3+3.(x)2.iy+3.x.(iy)2=u+iv
x3+i3y3+3x2iy+3xi2y2=u+iv
x3iy3+3x2iy3xy2=u+iv (i3=i  and  i2=1)
x33xy2+i(3x2yy3)=u+iv
On comparing real and imaginary part. we will get,
u=x33xy2   and   v=3x2yy3
Now,
ux+vy=x(x23y2)x+y(3x2y2)y
=x23y2+3x2y2
=4x24y2
=4(x2y2)
Hence proved

Question 11: If α and β are different complex numbers with |β|=1 , then find |βα1α¯β| .

Answer:

Let
α=a+ib and β=x+iy
It is given that
|β|=1x2+y2=1x2+y2=1
and
α¯=aib
Now,
|βα1α¯β|=|(x+iy)(a+ib)1(aib)(x+iy)|=|(xa)+i(yb)1(ax+iayibxi2yb)|
=|(xa)+i(yb)(1axyb)i(bxay)|
=(xa)2+(yb)2(1axyb)2+(bxay)2
=x2+a22xa+y2+b2yb1+a2x2+b2y22ax+2abxyby+b2x2+a2y22abxy
=(x2+y2)+a22xa+b2yb1+a2(x2+y2)+b2(x2+y2)2ax+2abxyby2abxy
=1+a22xa+b2yb1+a2+b22axby (x2+y2=1 given)
=1

Therefore, value of |βα1α¯β| is 1

Question 12: Find the number of non-zero integral solutions of the equation |1i|x=2x .

Answer:

Given problem is
|1i|x=2x
Now,
(12+(1)2)x=2x
(1+1)x=2x
(2)x=2x
2x2=2x
x2=x
x2=0
x = 0 is the only possible solution to the given problem

Therefore, there are 0 number of non-zero integral solutions of the equation |1i|x=2x

Question 13: If (a+ib)(c+id)(e+if)(g+ih)=A+iB, then show that (a2+b2)(c2+d2)(e2+f2)(g2+h2)=A2+B2

Answer:

It is given that
(a+ib)(c+id)(e+if)(g+ih)=A+iB,
Now, take mod on both sides
|(a+ib)(c+id)(e+if)(g+ih)|=|A+iB|
|(a+ib)||(c+id)||(e+if)||(g+ih)|=|A+iB| (|z1z2|=|z1||z2|)
(a2+b2)(c2+d2)(e2+f2)(g2+h2)=(A2+B2)
Square both the sides. we will get

(a2+b2)(c2+d2)(e2+f2)(g2+h2)=(A2+B2)

Hence proved

Question 14: If (1+i1i)m=1, then find the least positive integral value of m .

Answer:

Let
z=(1+i1i)m
Now, multiply both numerator and denominator by (1+i)
We will get,
z=(1+i1i×1+i1+i)m
=((1+i)212i2)m
=(12+i2+2i1+1)m
=(11+2i2)m (i2=1)
=(2i2)m
=im
We know that i4=1
Therefore, the least positive integral value of m is 4

Also read,


Topics covered in Chapter 4 Complex Numbers and Quadratic Equations Miscellaneous Exercise

Complex Numbers: Complex numbers are numbers that include both a real part and an imaginary part. They are written in the form a + bi, where i represents the square root of -1.

Algebraic Operations with Complex Numbers: Just like real numbers, complex numbers can be added, subtracted, multiplied, and divided using standard algebraic rules, while keeping in mind that i² = -1.

Modulus and Conjugate of Complex Numbers: The modulus represents the distance of a complex number from the origin on the Argand plane. The conjugate is formed by changing the sign of the imaginary part.

Argand Plane and Polar Representation: Complex numbers can be plotted on a plane with real and imaginary axes. They can also be expressed in polar form using their modulus and the angle they make with the positive real axis.

Quadratic Equations: These are second-degree equations in one variable. When their discriminant is negative, their solutions are complex numbers, which extend the idea of solving equations beyond real numbers.

Also read

NCERT Solutions of Class 11 Subject Wise

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Subject-Wise NCERT Exemplar Solutions

Use the links provided in the table below to get your hands on the NCERT exemplar solutions available for all the subjects.

Frequently Asked Questions (FAQs)

1. Who introduced the symbol i for root(-1)?

Euler introduced symbol i for root(-1) first time

2. Who represented a+ib as ordered pair (a, b)?

W,R. Hamilton

3. Find Z1.Z2 if Z1=a+ib and Z2=c+id

Z1Z2=(ac-bd)+i(ad+bc)

4. Is the statement “all real numbers are complex numbers” true?

Yes, the statement is true. Example: 1 can be written as 1+0i

5. What is the argument of (1+i)/(1-i)

The argument of (1+i)/(1-i) is pi/2

6. How many questions are given in the miscellaneous examples of Class 11 NCERT Maths chapter 4?

5 questions are solved in the miscellaneous examples of complex numbers and quadratic equations.

7. How many questions are given in NCERT solutions for Class 11 Maths chapter 5 miscellaneous exercise?

Twenty questions of miscellaneous exercise chapter 5 Class 11 are solved in the Class 11 Maths chapter 5 miscellaneous exercise solutions

8. Give the ordered pair of (1+i)/(1-i)?

(1+i)/(1-i)=i

So the ordered pair is (0,1)

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