NCERT Solutions for Class 9 Maths Chapter 2 Introduction to Linear Polynomials
NCERT Solutions help students understand concepts clearly, strengthen problem-solving skills, and prepare effectively for school and competitive exams. ALLEN's NCERT Solutions for Class 9 Maths Chapter 2 – Introduction to Linear Polynomials are based on the latest NCERT syllabus (2026–27) and are fully CBSE-aligned. Our expert-created, chapter-wise solutions provide step-by-step answers to every NCERT question, making learning simple and systematic. With free PDF downloads, students can learn anytime and build a strong foundation in algebra.
1.0Download NCERT Class 9 Maths Chapter 2 Introduction to Linear Polynomials Solutions
Class 9 Maths Chapter 2 – Introduction to Linear Polynomials introduces the fundamentals of polynomials, including variables, coefficients, constant terms, degree, linear patterns, functions, and simple linear relationships. Students can download the free PDF of NCERT Solutions for Class 9 Maths Chapter 2 for step-by-step solutions to every exercise, prepared according to the latest NCERT 2026–27 syllabus.
2.0Learning Outcomes - NCERT Class 9 Maths Chapter 2 Solutions
- Identify the variable, coefficient, constant term, and degree of a polynomial.
- Distinguish between constant, linear, quadratic, and cubic polynomials based on their degree.
- Understand the characteristics of a linear polynomial.
- Find the value of a polynomial by substituting the given value of the variable.
- Recognise and represent linear relationships using algebraic expressions.
- Understand functions as an input-output process through simple examples.
- Model real-life situations using linear growth and linear decay.
- Represent and interpret simple linear relationships using tables and graphs.
3.0Detailed Class 9 Maths Chapter 2 Introduction to Linear Polynomials Solutions
Exercise : 2.1
1.Find the degrees of the following polynomials:
(i) 2x2−5x+3
(ii) y3+2y−1
(iii) -9
(iv) 4z−3
Sol. (i) 2
(ii) 3
(iii) 0
(iv) 1
2. Write polynomials of degrees 1, 2 and 3 .
Sol. Degree 1 polynomials =2x+3,3x,9x−4 etc.
Degree 2 polynomials =2x2+3,3x2+2x, 9x2+2x+3 etc.
Degree 3 polynomials =3x3,4x3+2x2, 3x3+2x2+x+5 etc.
3. What are the coefficients of x2 and x3 in the polynomial x4−3x3+6x2−2x+7 ?
Sol. Coefficient of x2=6
Coefficient of x3=−3
4. What is the coefficient of z in the polynomial 4z3+5z2−11 ?
Sol. Coefficient of z=0
5. What is the constant term of the polynomial 9x3+5x2−8x−10 ?
Sol. Constant term =−10
Exercise: 2.2
1.Find the value of the linear polynomial 5x-3 if:
(i) x=0
(ii) x=−1
(iii) x=2
Sol. (i) Put x=0
5(0)−3=−3
(ii) Put x=−1
5(−1)−3=−5−3=−8
(iii) Put x=2
5(2)−3=10−3=7
2. Find the value of the quadratic polynomial 7s2−4s+6 if:
(i) s=0
(ii) s=−3
(iii) s=4
Sol. (i) Put s =0
7(0)2−4(0)+6=6
(ii) Puts =−3
7(−3)2−4(−3)+6=63+12+6=81
(iii) Put s=4
3.The present age of Salil's mother is three times Salil's present age. After 5 years, their ages will add up to 70 years. Find their present ages.
Sol. Let present age of Salil =x years and present age of Salil's mother will be = 3x years
After 5 years:
(x+5)+(3x+5)=70
4x+10=70
4x=60
x=15
Hence present age of Salil is 15 years and Salil's mother is 45 years.
4. The difference between two positive integers is 63. The ratio of the two integers is 2:5. Find the two integers.
Sol. Let two positive integers are x and x+63.
ATQ,
x+63x=52
5x=2x+126
3x=126
x=42
Hence the two integers are 42 and 105.
5. Ruby has 3 times as many two-rupee coins as she has five rupee- coins. If she has a total ₹88, how many coins does she have of each type?
Sol. Let number of five Rupee coins be =x and number of two Rupee coins will be =3x ATQ,
Value of five rupee coins =5x
and value of two rupee wins =2(3x)=6x
Given that 5x+6x=88
11x=88
x=8
Hence number of five rupee coins are 8 and number of two rupee coins are 24.
6. A farmer cuts a 300 feet fence into two pieces of different sizes. The longer piece is four times as long as the shorter piece. How long are the two pieces?
Sol. Let length of shorter piece =x feet So, length of longer piece will be =4x feet ATQ,
4x+x=300
5x=300
x=60
Hence, length of shorter piece is 60 feet and length of longer piece is 240 feet.
7. If the length of a rectangle is three more than twice its width and its perimeter is 24 cm , what are the dimensions of the rectangle?
Sol. Let width of rectangle be =xcm
So length of rectangle will be =2x+3 cm
Now, perimeter of rectangle =2(ℓ+b)
24=2[(2x+3)+x]
24=2[3x+3]
3x+3=12
3x=9
x=3
Hence length of rectangle is 9 cm and width of rectangle is 3 cm .
Exercise: 2.3
1.A student has ₹500 in her savings bank account. She gets ₹150 every month as pocket money. How much money will she have at the end of every month from the second month onwards? Find a linear expression to represent the amount she will have in the nth month.
Sol. Initial balance = ₹500
Monthly addition = ₹150
Month 1=500+150= ₹650
Month 2=650+150= ₹800
Month 3=800+150= ₹950
Month 4=950+150 = ₹1100
So, the expression is :
A=500+150n, where A is amount and n is number of months.
2.A rally starts with 120 members. Each hour, 9 members drop out of the group. How many members will remain after 1, 2,3,… hours? Find a linear expression to represent the number of members at the end of the nth hour.
Sol. Rally starts with 120 members and 9 members leave each hour. So,
After 1 hour = 120-9(1) = 111 members
After 2 hours = 120-9(2)=102 members
After 3 hours =120−9(3)=93 members
After 4 hours =120−9(4)=84 members
After 5 hours =120−9(5)=75 members
So, the expression is :
M=120−9n, where M is members and n is number of hours.
3. Suppose the length of a rectangle is 13 cm . Find the area if the breadth is (i) 12 cm , (ii) 10 cm , (iii) 8 cm . Find the linear pattern representing the area of the rectangle.
Sol. Length of Rectangle =13 cm (Given)
Area of Rectangle =ℓ×b
(i) b=12 cm
Area =13×12=156 cm2
(ii) b=10 cm
Area =13×10=130 cm2
(iii) b=8 cm
Area =13×8=104 cm2
So, the linear pattern is A=13 b, where A= Area and b= breadth.
4. Suppose the length of a rectangular box is 7 cm and breadth is 11 cm . Find the volume if the height is (i) 5 cm , (ii) 9 cm , (iii) 13 cm . Find the linear pattern representing the volume of the rectangular box.
Sol. Given, Length of Rectangular box =7 cm and breadth of Rectangular box =11 cm Volume of rectangle =ℓ×b×h
(i) h=5 cm
Volume =7×11×5=385 cm3
(ii) h=9 cm
Volume =7×11×9=693 cm3
(iii) h=13 cm
Volume =7×11×13=1001 cm3
So, the linear pattern is V=77 h, where V= Volume and h= height.
5. Sarita is reading a book of 500 pages. She reads 20 pages every day. How many pages will be left after 15 days? Express this as a linear pattern.
Sol. Total pages =500
Sarita reads every day = 20 pages
So, after 15 days =500−20(15)
=500−300
=200
So, the linear pattern is y=500−20x, where y= pages left and x= number of days.
Exercise : 2.4
1.Suppose a plant has height 1.75 feet and it grows by 0.5 feet each month.
(i) Find the height after 7 months.
(ii) Make a table of values for t varying from 0 to 10 months and show how the height, h , increases every month.
(iii) Find an expression that relates h and t , and explain why it represents linear growth.
Sol. Initial height =1.75 feet
Growth per month =0.5 feet
(i) Height after 7 months =1.75+0.5×7
=1.75+3.5
=5.25 feet
(ii)
(iii) Expressions is h=1.75+0.5t, where h= height and t= months.
It represents linear growth because the plant grows by the same fixed amount every month.
2. A mobile phone is bought for ₹10,000. Its value decreases by ₹800 every year.
(i) Find the value of the phone after 3 years.
(ii) Make a table of values for t varying from 0 to 8 years and show how the value of the phone, v, depreciates with time.
(iii) Find an expression that relates v and t , and explain why it represents linear decay.
Sol. Initial cost of mobile phone =₹10,000
Value decreases per year =₹800
(i) Value of phone after 3 years
=10,000−800×3=10,000−2400=₹7600
(ii)
(iii) Expression is V=10000−800t where V= value and t= time.
3. The initial population of a village is 750. Every year, 50 people move from a nearby city to the village.
(i) Find the population of the village after 6 years.
(ii) Make a table of values for t varying from 0 to 10 years and show how the population, P , increases every year.
(iii) Find an expression that relates P and t and explain why it represents linear growth.
Sol. Initial population of village =750
People move city to village per year =50
(i) Population after 6 years =750+50×6=750+300=1050
Sol. Given that y=ax+b
Case-I:
x=10,y=400
10a+b=400
⇒b=400−10a
Case-II:
x=14,y=500
14a+b=500
Put value of b from (i) to (ii)
14a+400−10a=500
4a=100
a=25 put this value to equation (i)
b=400−10(25)
b=150
2. A gym charges a fixed monthly fee and an additional cost per hour for using the badminton court. A student using the gym observed that when she used the badminton court for 10 hours, her bill was ₹ 800 . When she used it for 15 hours, her bill was ₹1100. If the monthly bill y depends on the hours of the use of the badminton court, x , according to the relation y=ax+b, find the values of a and b.
Sol. Given that y=ax+b
Case-I:
x=10,y=800
10a+b=800
⇒b=800−10a
Case-II:
x=15,y=1100
15a+b=1100
Put value of b from (i) to (ii)
15a+800−10a=1100
5a=300
a=60 put this value to equation (i)
b=800−10×60
b=800−600
b=200
3. Consider the relationship between temperature measured in degrees Celsius (∘C) and degrees Fahrenheit ( ∘F ), which is given by ∘C=a∘F+b. Find a and b , given that ice melts at 0 degrees Celsius and 32 degrees Fahrenheit, and water boils at 100 degrees Celsius and 212 degrees Fahrenheit. (Hint: When ∘C=0,∘F=32 and when ∘C=100,∘F=212. Use this information to find a and b , and thus, the linear relationship between ∘C and ∘F.)
Sol. Given that ∘C=a∘F+b
Case-I:
∘C=0,∘F=32
0=a×32+b
32a+b=0
b=−32a
Case-II:
∘C=100,∘F=212
100=a×212+b
212a+b=100
Put value of b from (i) to (ii)
212a−32a=100
180a=100
a=180100
a=95
Put this value to equation (i)
b=−32×95
b=−9160
Exercise : 2.6
1.Draw the graphs of the following sets of lines. In each case, reflect on the role of 'a' and 'b'.
(i) y=4x,y=2x,y=x
(ii) y=−6x,y=−3x,y=−x
(iii) y=5x,y=−5x
(iv) y=3x−1,y=3x,y=3x+1
(v) y=−2x−3,y=−2x,y=2x+3
Sol. (i) y=4x
Put x=0
y=4×0y=0
Put x=1
y=4×1y=4
y=2x
Put x=0
y=2×0y=0
Put x=1
y=2×1y=2
y=x
Put x=0
y=0
Put x=1
y=1
→b=0, that's why all three lines passes from origin.→ As 'a' increases from 1 to 2 to 4 the slope gets steeper.
(ii) y=−6x
Put x=0
y=−6×0y=0
Put x=1
y=−6×1y=−6
y=−3x
Put x=0
y=−3×0y=0
Put x=1
y=−3×1y=−3
y=−x Put x=0y=0
Put x=1
y=−1
→ b=0, that's why all three lines passes from origin.
→ Because 'a' values are negative they travel 'downhill' and because values gets larger the downhill drop becomes much steeper.
(iii) To draw the graph, we join points which lie on the line For y=5x Put x=0
y=5×0y=0
Put x=1
y=5×1y=5
For y Put xyy=−5x=0=−5×0=0 Put xyy=1=−5×1=−5
- These two lines have the exact same level of steepness because the number 5 is the same.
- The only difference is the sign. y=5x is a steep uphill climb, while y=−5x is a steep downhill drop.
(iv) To draw the graph, we join points which lie on the line For y=3x−1
Put x=0
y=3×0−1y=0−1y=−1
Put x=1
y=3×1−1y=3−1y=2
For y=3x
Put x=0
y=3×0y=0
Put x=1
y=3×1y=3
For y=3x+1
Put x=0
y=3×0+1y=0+1y=1
Put x=1
y=3×1+1y=3+1y=4
- Because the slope ' a ' is exactly the same for all three, they have the exact same steepness.
- This means they are parallel lines that will never touch.
- Changing the ' b ' value simply shifts the line vertically. y=3x goes through the center, y=3x+1 is shifted one unit up, and y=3x−1 is shifted one unit down.
(v) To draw the graph, we join points which lie on the line
For y=−2x−3
Put x=0
y=−2×0−3y=0−3y=−3
Put x=1
y=−2×1−3y=−2−3y=−5
For y=−2x
Put x=0
y=−2×0y=0
Put x=1
y=−2×1y=−2
For y=−2x+3
Put x=0
y=−2×0+3y=0+3y=3
Put x=1
y=−2×1+3y=−2+3y=1
Because the slope ' a ' is exactly the same for all three lines (-2), they all have the exact same "downhill" steepness.
Because they have the same steepness, they are perfectly parallel lines-they will never, ever intersect.
The 'b' values tell us how these parallel lines are stacked.
- The middle line (y=−2x) goes straight through the origin (0,0).
- The line y=−2x+3 is that exact same line, just shifted straight up like an elevator by 3 units.
- The line y=−2x−3 is shifted straight down by 3 units.
End of Chapter Exercise
1.Write a polynomial of degree 3 in the variable x, in which the coefficient of the x2 term is -7 .
Sol. 2x3−7x2+5x+30
2.Find the values of the following polynomials at the indicated values of the variables.
(i) 5x2−3x+7 if x=1
(ii) 4t3−t2+6 if t=a
Sol. (i) Let p(x)=5x2−3x+7
Putting x=1
p(1)=5(1)2−3(1)+7=5−3+7=9
(ii) Let p(t)=4t3−t2+6
Putting t=a
3.If we multiply a number by 25 and add 32 to the product, we get 12−7. Find the number.
Sol. Let Number be x
25×x+32=12−7
25x+32=12−7
25x=12−7−32
25x=12−7−8
25x=12−15
x=12−15×52
x=6−3
x=2−1
Hence the number is −21.
4.A positive number is 5 times another number. If 21 is added to both the numbers, then one of the new numbers becomes twice the other new number. What are the numbers?
Sol. Let the smaller number be x
Given that a positive number is 5 times another number.
Thus,
Positive number =5× Smaller number =5x
Now, 21 added to both numbers.
So, our numbers become:
New smaller number =x+21
New bigger number =5x+21
New bigger number =2× New smaller number
5x+21=2×(x+21)
5x+21=2x+42
5x−2x+21=42
3x+21=42
3x=42−21
3x=21
x=321
x=7
Thus, our numbers are
Smaller number =x=7
Bigger number =5x=5×7=35
5. If you have ₹ 800 and you save ₹ 250 every month, find the amount you have after (i) 6 months (ii) 2 years. Express this as a linear pattern.
Sol. (i) Thus,
Initial Value = ₹ 800
Value after 1 month =800+250
= ₹ 1,050
Value after 2 months =800+250×2
=800+500= ₹ 1,300
Value after 3 months =800+250×3
=800+750=₹1,550
Similarly, we can write
Value after 6 months =800+250×6
=800+1500=₹2,300
(ii) We also need to find value after 2 years
Since 2 years =2×12 months
=24 months
We can write
Value after 2 years = Value after 24 months
=800+250×24
=800+6,000=₹6,800
We are also asked to express it as a linear pattern
Let time in months =t
And, value of money (in ₹) after t months be v(t)
Since value v starts at ₹ 800 and adds ₹250 every month t.
Our Expression is v(t)=800+250t
4.0Important Key Concepts of NCERT Solutions for Class 9 Maths Chapter 2
5.0Exercise-wise NCERT Class 9 Maths Chapter 2 - Introduction to Linear polynomials
Get a quick overview of the concepts covered in each exercise of NCERT Class 9 Maths Chapter 2 – Introduction to Linear Polynomials. This exercise-wise summary helps build conceptual clarity and makes revision more focused and effective.
6.0Quick Revision on Class 9 Maths Chapter 2 - Introduction to Linear Polynomials
7.0Related Study Materials Class 9 Maths
Improve your concepts and prepare confidently for school and CBSE exams with ALLEN’s Class 9 Maths study materials designed based on the NCERT Solutions. along with the the latest syllabus, NCERT textbooks, revision notes, sample papers and previous years’ question papers to improve your learning.
8.0Advantages of Chapter 2 Maths Class 9 NCERT Solutions
- Identifies Linear Polynomials: Enables students to identify linear polynomials by degree, coefficients and constant terms.
- Explains Polynomial Structure: Builds understanding of variables, coefficients, and the degree of a polynomial.
- Teaches Evaluation Skills: Shows how to evaluate a linear polynomial by substituting different values for the variable.
- Builds Graph Interpretation: It explains how linear polynomials are represented as graphs of straight lines.
- Develops Understanding of Linear Relationships Illustrates the use of linear polynomials to express mathematical relationships.
- Builds a strong foundation Prepares Students for Linear Equations, Functions, and Higher Algebraic Concepts