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NCERT Solutions for Class 12 Maths Chapter 9 Exercise 9.2 - Differential Equations

NCERT Solutions for Class 12 Maths Chapter 9 Exercise 9.2 - Differential Equations

Edited By Komal Miglani | Updated on May 08, 2025 02:27 PM IST | #CBSE Class 12th

Suppose you are watching the way a drug dissolves in your blood after some time. The rate of variation of the concentration can be described by a differential equation. These real-life situations, in which the rate of change is dependent on the quantity itself, are the best examples of how the general and particular solutions of differential equations are used.

NCERT Solutions for Class 12 Maths Chapter 9 – Exercise 9.2 are explained in a plain, step-by-step manner so that the students can easily understand these important concepts. The NCERT solutions are prepared by experienced mathematics faculty members of Careers360, strictly following the CBSE 2025–26 syllabus. In NCERT solution for Class 12 Maths Chapter 9 Exercise 9.2 students learn the difference between a general solution (with arbitrary constants) and a particular solution (obtained after assigning definite constants), differentiating and integrating to move between solutions and equations, and apply the basic concepts learned in Exercise 9.1 to more practical solution problem scenarios. Proper practice of these exercises not only increases confidence for board exams but is also beneficial for competitive exams such as the JEE.

This Story also Contains
  1. Class 12 Maths Chapter 9 Exercise 9.2 Solutions: Download PDF
  2. NCERT Solutions Class 12 Maths Chapter 9: Exercise 9.2
  3. Question:1 Verify that the given functions (explicit or implicit) is a solution of the corresponding differential equation:
  4. Topics covered in Chapter 9 Differential Equation: Exercise 9.2
  5. NCERT Solutions Subject Wise
  6. Subject Wise NCERT Exemplar Solutions

Class 12 Maths Chapter 9 Exercise 9.2 Solutions: Download PDF

This material provides easy solutions to all the questions of Exercise 9.2 of Differential Equations. The PDF can be downloaded by the students for practice and enhancement of the chapter for board and and competitive exams

Download PDF

NCERT Solutions Class 12 Maths Chapter 9: Exercise 9.2

Question:1 Verify that the given functions (explicit or implicit) is a solution of the corresponding differential equation:

y=ex+1: yy=0

Answer:

Given,

y=ex+1

Now, differentiating both sides w.r.t. x,

dydx=dexdx=ex

Again, differentiating both sides w.r.t. x,

dydx=dexdx=ex

y=ex

Substituting the values of y’ and y'' in the given differential equations,

y'' - y' = e x - e x = 0 = RHS.

Therefore, the given function is the solution of the corresponding differential equation.

Question:2 Verify that the given functions (explicit or implicit) is a solution of the corresponding differential equation:

y=x2+2x+C: y2x2=0

Answer:

Given,

y=x2+2x+C

Now, differentiating both sides w.r.t. x,

dydx=ddx(x2+2x+C)=2x+2

Substituting the values of y’ in the given differential equations,

y2x2=2x+22x2=0=RHS .

Therefore, the given function is the solution of the corresponding differential equation.

Question:3. Verify that the given functions (explicit or implicit) is a solution of the corresponding differential equation:

y=cosx+C: y+sinx=0

Answer:

Given,

y=cosx+C

Now, differentiating both sides w.r.t. x,

dydx=ddx(cosx+C)=sinx

Substituting the values of y’ in the given differential equations,

ysinx=sinxsinx=2sinxRHS .

Therefore, the given function is not the solution of the corresponding differential equation.

Question:4. Verify that the given functions (explicit or implicit) is a solution of the corresponding differential equation:

y=1+x2: y=xy1+x2

Answer:

Given,

y=1+x2

Now, differentiating both sides w.r.t. x,

dydx=ddx(1+x2)=2x21+x2=x1+x2

Substituting the values of y in RHS,

x1+x21+x2=x1+x2=LHS .

Therefore, the given function is a solution of the corresponding differential equation.

Question:5 Verify that the given functions (explicit or implicit) is a solution of the corresponding differential equation:

y=Ax: xy=y(x0)

Answer:

Given,

y=Ax

Now, differentiating both sides w.r.t. x,

dydx=ddx(Ax)=A

Substituting the values of y' in LHS,

xy=x(A)=Ax=y=RHS .

Therefore, the given function is a solution of the corresponding differential equation.

Question:6. Verify that the given functions (explicit or implicit) is a solution of the corresponding differential equation:

y=xsinx: xy=y+xx2y2 (x0 and x>y or x<y)

Answer:

Given,

y=xsinx

Now, differentiating both sides w.r.t. x,

dydx=ddx(xsinx)=sinx+xcosx

Substituting the values of y' in LHS,

xy=x(sinx+xcosx)

Substituting the values of y in RHS.

xsinx+xx2x2sin2x=xsinx+x21sinx2=x(sinx+xcosx)=LHS

Therefore, the given function is a solution of the corresponding differential equation.

Question:7 Verify that the given functions (explicit or implicit) is a solution of the corresponding differential equation:

xy=logy+C: y=y21xy (xy1)

Answer:

Given,

xy=logy+C

Now, differentiating both sides w.r.t. x,

y+xdydx=ddx(logy)=1ydydx \ \

y2+xyy=y

y2=y(1xy)

y=y21xy

Substituting the values of y' in LHS,

y=y21xy=RHS

Therefore, the given function is a solution of the corresponding differential equation.

Question:8 In each of the Exercises 1 to 10 verify that the given functions (explicit or implicit) is a solution of the corresponding differential equation:

ycosy=x:( ysiny+cosy+x)y=y

Answer:

Given,

ycosy=x

Now, differentiating both sides w.r.t. x,

dydx+sinydydx=ddx(x)=1

y' + siny.y' = 1

y'(1 + siny) = 1

y=11+siny

Substituting the values of y and y' in LHS,

( (x+cosy)siny+cosy+x)(11+siny)

=[x(1+siny)+cosy(1+siny)]11+siny

= (x + cosy) = y = RHS

Therefore, the given function is a solution of the corresponding differential equation.

Question:9 Verify that the given functions (explicit or implicit) is a solution of the corresponding differential equation:

x+y=tan1y: y2y+y2+1=0

Answer:

Given,

x+y=tan1y

Now, differentiating both sides w.r.t. x,

1+dydx=11+y2dydx

1+y2=y(1(1+y2))=y2y

y=1+y2y2

Substituting the values of y' in LHS,

y2(1+y2y2)+y2+1=1y2+y2+1=0=RHS

Therefore, the given function is a solution of the corresponding differential equation.

Question:10 Verify that the given functions (explicit or implicit) is a solution of the corresponding differential equation:

y=a2x2 x(a,a): x+ydydx=0 (y0)

Answer:

Given,

y=a2x2

Now, differentiating both sides w.r.t. x,

dydx=ddx(a2x2)=2x2a2x2=xa2x2

Substituting the values of y and y' in LHS,

x+ydydx=x+(a2x2)(xa2x2)=0=RHS

Therefore, the given function is a solution of the corresponding differential equation.

Question:11 The number of arbitrary constants in the general solution of a differential equation of fourth order are:
(A) 0
(B) 2
(C) 3
(D) 4

Answer:

(D) 4

The number of constants in the general solution of a differential equation of order n is equal to its order.

Question:12 The number of arbitrary constants in the particular solution of a differential equation of third order are:
(A) 3
(B) 2
(C) 1
(D) 0

Answer:

(D) 0

In a particular solution of a differential equation, there is no arbitrary constan


Also check -

Background wave

Topics covered in Chapter 9 Differential Equation: Exercise 9.2

TopicDescriptionExample
General SolutionA solution with general constants that determine a class of curves.y=Cex is a general solution of dydx=y
Particular SolutionA specific solution obtained by giving a particular value to the arbitrary constant(s).If y=Cex and y=2 when x=0, then C=2, so y= 2ex
Arbitrary ConstantsConstants that are used in integration. Used to represent general solutions.C in y=Cex
Formulating Differential EquationsMaking of a differential equation from a known general solution by eliminating the arbitrary constants.Given: y=Aex+Bex, eliminate A and B to form the DE.
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Frequently Asked Questions (FAQs)

1. What is the number of examples given in the topic 9.3 of Class 12 NCERT Mathematics Book?

Two examples are given to understand the concepts explained in exercise 9.3.

2. How many exercises are there in NCERT solutions for Class 12 Maths chapter 9?

A total of 7 exercises including the miscellaneous are there in the chapter differential equation.

3. How many questions are covered in exercise 9.2?

12 questions are discussed in the Class 12th Maths chapter 6 exercise 9.2 .

4. Whether the chapter differential equations is important for the Class 12 exam?

Yes. Solving Exercise 9.2 Class 12 Maths is necessary to prepare for the board exam of Class 12.

5. What are some basics knowledge required to solve the questions in differential equations?

The knowledge of differentiation and integration is required.

6. What is the topic after exercise 9.2?

Topic 9.4 is about how to form a differential equation if the general solutions are given.

7. Why solve exercise 9.1?

It is necessary to understand the basics before proceeding with the chapter. Exercise 9.1 gives a good knowledge of the degree and order of differential equations. So it is necessary to solve this exercise

8. Is it necessary to solve exercise 9.2?

Yes. To understand the concepts discussed in topic 9.3 it is necessary to solve exercise 9.2  

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A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is

Option 1)

0.34\; J

Option 2)

0.16\; J

Option 3)

1.00\; J

Option 4)

0.67\; J

A person trying to lose weight by burning fat lifts a mass of 10 kg upto a height of 1 m 1000 times.  Assume that the potential energy lost each time he lowers the mass is dissipated.  How much fat will he use up considering the work done only when the weight is lifted up ?  Fat supplies 3.8×107 J of energy per kg which is converted to mechanical energy with a 20% efficiency rate.  Take g = 9.8 ms−2 :

Option 1)

2.45×10−3 kg

Option 2)

 6.45×10−3 kg

Option 3)

 9.89×10−3 kg

Option 4)

12.89×10−3 kg

 

An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range

Option 1)

2,000 \; J - 5,000\; J

Option 2)

200 \, \, J - 500 \, \, J

Option 3)

2\times 10^{5}J-3\times 10^{5}J

Option 4)

20,000 \, \, J - 50,000 \, \, J

A particle is projected at 600   to the horizontal with a kinetic energy K. The kinetic energy at the highest point

Option 1)

K/2\,

Option 2)

\; K\;

Option 3)

zero\;

Option 4)

K/4

In the reaction,

2Al_{(s)}+6HCL_{(aq)}\rightarrow 2Al^{3+}\, _{(aq)}+6Cl^{-}\, _{(aq)}+3H_{2(g)}

Option 1)

11.2\, L\, H_{2(g)}  at STP  is produced for every mole HCL_{(aq)}  consumed

Option 2)

6L\, HCl_{(aq)}  is consumed for ever 3L\, H_{2(g)}      produced

Option 3)

33.6 L\, H_{2(g)} is produced regardless of temperature and pressure for every mole Al that reacts

Option 4)

67.2\, L\, H_{2(g)} at STP is produced for every mole Al that reacts .

How many moles of magnesium phosphate, Mg_{3}(PO_{4})_{2} will contain 0.25 mole of oxygen atoms?

Option 1)

0.02

Option 2)

3.125 × 10-2

Option 3)

1.25 × 10-2

Option 4)

2.5 × 10-2

If we consider that 1/6, in place of 1/12, mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will

Option 1)

decrease twice

Option 2)

increase two fold

Option 3)

remain unchanged

Option 4)

be a function of the molecular mass of the substance.

With increase of temperature, which of these changes?

Option 1)

Molality

Option 2)

Weight fraction of solute

Option 3)

Fraction of solute present in water

Option 4)

Mole fraction.

Number of atoms in 558.5 gram Fe (at. wt.of Fe = 55.85 g mol-1) is

Option 1)

twice that in 60 g carbon

Option 2)

6.023 × 1022

Option 3)

half that in 8 g He

Option 4)

558.5 × 6.023 × 1023

A pulley of radius 2 m is rotated about its axis by a force F = (20t - 5t2) newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg m2 , the number of rotations made by the pulley before its direction of motion if reversed, is

Option 1)

less than 3

Option 2)

more than 3 but less than 6

Option 3)

more than 6 but less than 9

Option 4)

more than 9

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