Class 9 · Maths · Chapter 2 · बिहार बोर्ड (BSEB)CBSE · NCERT 2026-27

Polynomials

Polynomials

How to use this page:
1. Read — 2.1 degree · 2.2 zeroes · 2.3 remainder · 2.4 factors · 2.5 identities, diagram, worked example, board tip
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4. The memory figure is the square of (a+b), split into a², b² and two ab rectangles.

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  • 1 A polynomial in one variable and its degree — Exercise 2.1
  • 2 The value of a polynomial and its zeroes — Exercise 2.2
  • 3 Division and the Remainder Theorem — Exercise 2.3
  • 4 The Factor Theorem and factorisation — Exercise 2.4
  • 5 The first four identities — Exercise 2.5
  • 6 Identities for three terms and cubes — Exercise 2.5
  • Chapter winner — every lesson at mastery ★

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1

A polynomial in one variable and its degree — Exercise 2.1

एक चर का बहुपद और घात — प्रश्नावली 2.1 · NCERT 2.2 · Exercise 2.1

New
A polynomial in one variable and its degreexy
Read the numbers on the axes, then join the points — the line is the picture of the equation.
The exponent must be a whole numberNotes

A polynomial in one variable x is p(x) = aₙxⁿ + aₙ₋₁xⁿ⁻¹ + … + a₁x + a₀, with aₙ ≠ 0. Here n is a whole number. a₀, a₁, … are the coefficients. The terms run from aₙxⁿ down to a₀.

One term is a monomial, two terms a binomial, three terms a trinomial. Degree 1 is linear, of the form ax + b with a ≠ 0. Degree 2 is quadratic. Degree 3 is cubic. 5x² + 3x + π is quadratic, because π may be a coefficient.

x + 1/x = x + x⁻¹ is not a polynomial. Neither is √x + 4 = x1/2 + 4. A non-zero constant has degree 0. The degree of the zero polynomial is not defined.

NameDegreeExample
Constant07
Linear14x + 7
Quadratic2x² − 3x + 2
Cubic32x³ − x
Worked exampleExample

Question: Find the degree of 2 − y² − y³ + 2y⁸. Also write the degree of the constant 5.

Step 1. Write the terms in descending degree: 2y⁸ − y³ − y² + 2.

Step 2. The highest power of the variable is 8. So the degree is 8.

Step 3. 5 is a non-zero constant. It has no variable, which means the coefficient of y⁰. The degree is 0.

Caution: If the polynomial is only 0, do not write a degree. It is not defined.

10-second revision
  • Degree = the highest power
  • A non-zero constant has degree 0
  • 1/x and √x are not polynomials
Board tip · BSEBBoard tip

Before division, and when the degree is asked, arrange the terms in descending degree.

Board tip · CBSEBoard tip

A coefficient may be irrational. πx² + 2 is a polynomial. The degree belongs to the variable, not to the coefficient.

Check your understandingall correct = mastery ★
1
Which of these is a polynomial?
Check
2
The degree of the zero polynomial is 0.
Check
3
The degree of 4x + 7 is ______.
Check
4
x² + 3x + 2 is —
Check
5
Say why 5x² + 3x + π is a polynomial and why √x + 1 is not. Write the degree where it exists.
Check3 marks
Next lesson →
2

The value of a polynomial and its zeroes — Exercise 2.2

बहुपद का मान और शून्यक — प्रश्नावली 2.2 · NCERT 2.3 · Exercise 2.2

New
The value of a polynomial and its zeroesThe parabola cuts the x-axis at the zeroes
The graph of a quadratic is a parabola. It cuts the x-axis at its zeroes.
p(c) = 0 is the zeroNotes

The number obtained by putting c in place of x in p(x) is p(c). If p(c) = 0, then c is a zero of the polynomial. The same c is a root of the equation p(x) = 0.

The linear polynomial ax + b has exactly one zero, x = −b/a. A non-zero constant has no zero, because 7 = 0 never holds. Every real number is a zero of the zero polynomial. That is the convention.

A polynomial can have more than one zero. The zeroes of x² − 2x are 0 and 2, because x(x − 2) = 0.

Worked exampleExample

Question: Find one zero of p(x) = 2x + 1 and check it.

Step 1. For a zero put p(x) = 0: 2x + 1 = 0.

Step 2. 2x = −1, so x = −1/2.

Formula: The zero of ax + b is −b/a. Here a = 2 and b = 1, so −b/a = −1/2.

Check: p(−1/2) = 2×(−1/2) + 1 = −1 + 1 = 0. So −1/2 is a zero.

10-second revision
  • A zero means p(c) = 0
  • A linear has one zero, −b/a
  • A non-zero constant has no zero
Board tip · BSEBBoard tip

The zero of x + 2 is −2, not 2. The sign flips.

Board tip · CBSEBoard tip

Value and zero are different. p(1) may be 4. A zero is only where the value is 0.

Check your understandingall correct = mastery ★
1
The zero of p(x) = x − 3 is —
Check
2
The constant polynomial 4 has no zero.
Check
3
If p(x) = 5x − 4x² + 3, then p(0) = ______.
Check
4
Check that −2 is a zero of p(x) = x + 2 and that 2 is not. Write both values.
Check2 marks
Next lesson →
3

Division and the Remainder Theorem — Exercise 2.3

भाग और शेषफल प्रमेय — प्रश्नावली 2.3 · NCERT 2.4 · Exercise 2.3

New
Division and the Remainder Theoremxy
Read the numbers on the axes, then join the points — the line is the picture of the equation.
The remainder is p(a)Notes

Polynomials are divided in the same spirit as numbers. In 15 = (6 × 2) + 3 the remainder is smaller than the divisor. For polynomials, p(x) = g(x) q(x) + r(x), and the degree of r is less than the degree of g.

If the divisor is a monomial, divide each term. Dividing 2x³ + x² + x by x gives 2x² + x + 1. But in 3x² + x + 1 the constant 1 does not divide by x into a polynomial term. The remainder stays 1 and x is not a factor.

Before dividing, write descending powers. Write x + 3x² − 1 as 3x² + x − 1. If the degree is at least 1 and the divisor is x − a, the remainder is p(a).

Worked exampleExample

Question: Find the remainder when p(x) = x³ + 1 is divided by x + 1. Also show the long division.

Formula: x + 1 = x − (−1), so a = −1 and the remainder is p(−1).

Substitution: p(−1) = (−1)³ + 1 = −1 + 1 = 0.

Long division: The dividend is x³ + 0x² + 0x + 1. The first term is x². (x + 1)x² = x³ + x². Subtraction leaves −x². The next term is −x. (x + 1)(−x) = −x² − x. Subtraction leaves x. The next term is +1. (x + 1)(1) = x + 1. Subtraction leaves 0.

Answer: The quotient is x² − x + 1 and the remainder is 0. The two methods agree.

10-second revision
  • Remainder = p(a), divisor x − a
  • x + 1 means a = −1
  • If the remainder is 0, the divisor is a factor
Board tip · BSEBBoard tip

For x − 1 and x + 1 the value of a is different. Use p(1) for x − 1 and p(−1) for x + 1.

Board tip · CBSEBoard tip

Write a missing power with coefficient 0, such as x² and x in x³ + 1.

Check your understandingall correct = mastery ★
1
The remainder when p(x) = x² − 4 is divided by x − 2 is —
Check
2
The remainder on division by x + 1 is p(1).
Check
3
If p(x) = x³ − 1 and the divisor is x − 1, the remainder is ______.
Check
4
Before division, x + 3x² − 1 is written as —
Check
5
Dividing 2x³ + x² + x by x gives the quotient ______.
Check
6
Find the remainder when p(x) = x⁴ + x³ − 2x² + x + 1 is divided by x − 1. Write the formula and the substitution.
Check3 marks
Next lesson →
4

The Factor Theorem and factorisation — Exercise 2.4

गुणनखंड प्रमेय और गुणनखंडन — प्रश्नावली 2.4 · NCERT 2.5 · Exercise 2.4

New
The Factor Theorem and factorisationThe parabola cuts the x-axis at the zeroes
The graph of a quadratic is a parabola. It cuts the x-axis at its zeroes.
p(a) = 0 means a factorNotes

By the Remainder Theorem, p(x) = (x − a) q(x) + p(a). If p(a) = 0, then p(x) = (x − a) q(x). (x − a) is a factor if and only if p(a) = 0.

Split the middle term of ax² + bx + c into two numbers whose product is a×c and whose sum is b. Then take out the common bracket.

For a cubic, try factors of the constant. If p(1) = 0, then (x − 1) is a factor. Divide, leave a quadratic, and split that too.

Worked exampleExample

Question: Factorise 6x² + 17x + 5 by splitting the middle term.

Step 1. a×c = 6×5 = 30 and b = 17. The two numbers are 15 and 2, because 15×2 = 30 and 15+2 = 17.

Step 2. 6x² + 15x + 2x + 5.

Step 3. 3x(2x + 5) + 1(2x + 5) = (3x + 1)(2x + 5).

Check: (3x + 1)(2x + 5) = 6x² + 15x + 2x + 5 = 6x² + 17x + 5.

10-second revision
  • p(a) = 0 means (x − a) is a factor
  • Middle term: product ac, sum b
  • 6x² + 17x + 5 = (3x + 1)(2x + 5)
Board tip · BSEBBoard tip

If the question asks about the factor x + 2, put a = −2 and look at p(−2).

Board tip · CBSEBoard tip

The signs of the split numbers follow the sum. If the sum is negative, both can be negative.

Check your understandingall correct = mastery ★
1
x + 2 is a factor of x³ + 3x² + 5x + 6, because —
Check
2
y² − 5y + 6 = (y − 2)(y − 3).
Check
3
If x − 1 is a factor of p(x), then p(1) = ______.
Check
4
One factor of x² + 5x + 6 is —
Check
5
For p(x) = x³ − 6x² + 11x − 6, find p(1) and say whether x − 1 is a factor.
Check2 marks
Next lesson →
5

The first four identities — Exercise 2.5

पहली चार सर्वसमिकाएँ — प्रश्नावली 2.5 · NCERT 2.6 · Exercise 2.5 · (a+b)²

New
True for every valueNotes

An identity is an algebraic equality that is true for every value of the variables. The first four:

I. (x + y)² = x² + 2xy + y²

II. (x − y)² = x² − 2xy + y²

III. x² − y² = (x + y)(x − y)

IV. (x + a)(x + b) = x² + (a + b)x + ab

A square of side (a + b) splits into a², ab, ab and b², so (a + b)² = a² + 2ab + b². These work both for products and for factors.

Four parts of (a+b)²a²ababb²abab(a+b)²= a² + ab+ ab + b²= a² + 2ab + b²The two ab rectangles make 2ab.
Figure: the large square splits into a², two ab rectangles and b². The sum is a² + 2ab + b².
Worked exampleExample

Question: Find 103 × 98 without multiplying directly.

Step 1. 103 = 100 + 3 and 98 = 100 + (−2).

Formula IV: (x + a)(x + b) = x² + (a + b)x + ab. Here x = 100, a = 3, b = −2.

Substitution: 100² + (3 + (−2))×100 + (3)(−2).

Step 2. 10000 + 1×100 + (−6) = 10000 + 100 − 6 = 10094.

Check: 103×100 − 103×2 = 10300 − 206 = 10094.

10-second revision
  • (a+b)² = a² + 2ab + b²
  • x² − y² = (x+y)(x−y)
  • (x+a)(x+b) = x² + (a+b)x + ab
Board tip · BSEBBoard tip

See 49a² + 70ab + 25b² as (7a + 5b)². First spot the squares and the double product.

Board tip · CBSEBoard tip

For a product without direct multiplication, choose numbers near 100, then use Identity IV.

Check your understandingall correct = mastery ★
1
(x + 3)² equals —
Check
2
(x − y)² = x² − y².
Check
3
x² − 9 = (x + 3)(______ ).
Check
4
(x − 3)(x + 5) equals —
Check
5
The figure of (a + b)² has two parts labelled ab.
Check
6
Factorise 49a² + 70ab + 25b² by an identity. Write the steps.
Check3 marks
Next lesson →
6

Identities for three terms and cubes — Exercise 2.5

तीन पद और घन की सर्वसमिकाएँ — प्रश्नावली 2.5 · NCERT 2.6 · Exercise 2.5 · cubes

New
Identities for three terms and cubes(a + b)²= a² + 2ab + b²
The picture of (a+b)²: the square of a, the square of b, and two rectangles ab.
From V to VIIINotes

V. (x + y + z)² = x² + y² + z² + 2xy + 2yz + 2zx. It is obtained from (a + b)² by treating (x + y) as one term.

VI. (x + y)³ = x³ + y³ + 3xy(x + y)

VII. (x − y)³ = x³ − y³ − 3xy(x − y)

VIII. x³ + y³ + z³ − 3xyz = (x + y + z)(x² + y² + z² − xy − yz − zx)

If x + y + z = 0, then x³ + y³ + z³ = 3xyz. The expanded form is the right-hand side. The left-hand side is the compact form.

Worked exampleExample

Question: Expand (2x + 1)³.

Formula VI: (x + y)³ = x³ + y³ + 3xy(x + y). Here the first term is 2x and the second is 1.

Substitution: (2x)³ + 1³ + 3(2x)(1)(2x + 1).

Step 1. 8x³ + 1 + 6x(2x + 1).

Step 2. 6x(2x + 1) = 12x² + 6x.

Answer: 8x³ + 12x² + 6x + 1.

10-second revision
  • (x+y+z)² has three squares and three double products
  • (x+y)³ = x³ + y³ + 3xy(x+y)
  • x+y+z = 0 implies x³+y³+z³ = 3xyz
Board tip · BSEBBoard tip

In an expansion of three squares, write all of 2xy, 2yz and 2zx. Leaving one out loses marks.

Board tip · CBSEBoard tip

If you see x + y + z = 0, the cubes are directly 3xyz. Open the full Identity VIII only when the sum is not zero.

Check your understandingall correct = mastery ★
1
If x + y + z = 0, then x³ + y³ + z³ equals —
Check
2
(x − y)³ = x³ − y³ − 3xy(x − y).
Check
3
In (x + y + z)² the term in xy is ______xy.
Check
4
Given 3 + (−2) + (−1) = 0. Find x³ + y³ + z³ and check with 3xyz.
Check3 marks
Question bank →

❓ Full question bank — with answers and explanations — 59 questions

No question is marked as a verified past paper. The BSEB set is a model for practice. CBSE items are CBSE-style, not a copy of any year’s paper.

Multiple choice

0/12
Pick one option. A wrong try brings a hint.
1
This is not a polynomial —
Board-style (practice)1 mark
2
The degree of 2y⁸ − y³ + 2 is —
Board-style (practice)1 mark
3
A linear polynomial has one zero. The zero of 3x − 6 is —
Board-style (practice)1 mark
4
One zero of p(x) = x² − 5x + 6 is —
Board-style (practice)1 mark
5
On division by x − 1 the remainder is —
Board-style (practice)1 mark
6
Dividing x³ + 1 by x + 1 leaves remainder —
Board-style (practice)1 mark
7
One factor of 6x² + 17x + 5 is —
Board-style (practice)1 mark
8
The middle term of (x + 4)² is —
Board-style (practice)1 mark
9
x² − 16 equals —
Board-style (practice)1 mark
10
In (x + y + z)² the coefficient of xy is —
Board-style (practice)1 mark
11
If x + y + z = 0, then x³ + y³ + z³ is —
Board-style (practice)1 mark
12
What is correct about the zero polynomial?
Board-style (practice)1 mark
↑ Question hub

True or false

0/6
1
5 is a polynomial and its degree is 0.
Board-style (practice)1 mark
2
Every linear polynomial has two zeroes.
Board-style (practice)1 mark
3
If the remainder is 0, the divisor is a factor.
Board-style (practice)1 mark
4
(x − y)² = x² − 2xy + y².
Board-style (practice)1 mark
5
(x + y)² = x² + y².
Board-style (practice)1 mark
6
(x + y + z) is a factor of x³ + y³ + z³ − 3xyz.
Board-style (practice)1 mark
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Fill in the blanks

0/6
1
The degree of a quadratic polynomial is ______.
Board-style (practice)1 mark
2
The zero of ax + b is ______.
Board-style (practice)1 mark
3
The remainder on division by x + 3 is p(______).
Board-style (practice)1 mark
4
x² + 7x + 12 = (x + 3)(x + ______ ).
Board-style (practice)1 mark
5
(a + b)² = a² + ______ + b².
Board-style (practice)1 mark
6
If x + y + z = 0, then x³ + y³ + z³ = ______.
Board-style (practice)1 mark
↑ Question hub

Match

0/2
1
Match the polynomial with its name.
Board-style (practice)2 marks
Column B: A. Quadratic · B. Cubic · C. Constant · D. Linear
1. 7
2. 4x + 1
3. x² + 1
4. x³ − x
2
Match the identity with its left side.
NCERT-style · practice2 marks
Column B: A. (x+y)(x−y) · B. x³+y³+3xy(x+y) · C. 3xyz · D. x²+2xy+y²
1. (x+y)²
2. x²−y²
3. (x+y)³
4. Cubes when x+y+z=0
↑ Question hub

Assertion–reason

0/4
Check both statements, then see whether the reason explains the assertion.
1

Assertion (A): x − 2 is a factor of p(x) = x² − 4.

Reason (R): p(2) = 0.

Board-style (practice)1 mark
2

Assertion (A): The degree of 5 is 0.

Reason (R): The degree of the zero polynomial is also 0.

Board-style (practice)1 mark
3

Assertion (A): (x + 1)² = x² + 2x + 1.

Reason (R): (x + 1)² = x² + 1.

Board-style (practice)1 mark
4

Assertion (A): x + 1/x is a polynomial.

Reason (R): In a polynomial every power of the variable is a whole number.

Board-style (practice)1 mark
↑ Question hub

Coefficient practice

0/4

These equations are not results of this maths chapter. This is only practice in filling coefficients. A blank coefficient means 1.

1
This is coefficient practice, not a result of the polynomials chapter. H2 + O2 makes water. Balance by filling coefficients (blank = 1).
Board-style (practice)1 mark
H2 + O2 → H2O
2
This is coefficient practice, not a result of the polynomials chapter. N2 + H2 makes NH3. Balance by filling coefficients (blank = 1).
Board-style (practice)1 mark
N2 + H2 → NH3
3
This is coefficient practice, not a result of the polynomials chapter. C + O2 makes CO2. Balance by filling coefficients (blank = 1).
Board-style (practice)1 mark
C + O2 → CO2
4
This is coefficient practice, not a result of the polynomials chapter. H2 + Cl2 makes HCl. Balance by filling coefficients (blank = 1).
Board-style (practice)1 mark
H2 + Cl2 → HCl
↑ Question hub

Classify

0/2
1
Place each expression as a polynomial or not.
Board-style (practice)2 marks
3x² + 1
x + 1/x
7
√x + 2
2
Choose the degree class.
NCERT-style · practice2 marks
4x + 7
x² + 1
2x³ − x
0
↑ Question hub

Very short answer

0/4
1
Define the degree of a polynomial in one line.
Board-style (practice)1 mark
2
Find the zeroes of p(x) = x² − 2x.
Board-style (practice)2 marks
3
State the Remainder Theorem.
NCERT-style · practice2 marks
4
Write the expansion of (x + y)².
Board-style (practice)1 mark
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Short answer

0/4
1
Find the remainder when p(x) = 2x³ − x² + 4 is divided by x − 1.
Board-style (practice)3 marks
2
Factorise y² − 5y + 6.
NCERT-style · practice3 marks
3
Find 105 × 106 by an identity.
Board-style (practice)3 marks
4
Write the expansion of (3a + 4b + 5c)² without multiplying everything out by hand.
Board-style (practice)3 marks
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Long answer

0/3
1
Write the idea of the Remainder Theorem. Then divide x³ + 1 by x + 1 and find both the remainder and the quotient.
Board-style (practice)5 marks
2
Explain the figure of (a+b)² in four parts. Then write the factors of 49a² + 70ab + 25b².
NCERT-style · practice5 marks
3
Write Identity VIII. Then show that for 3, −2 and −1 the sum of cubes equals 3xyz.
Board-style (practice)5 marks
↑ Question hub

BSEB model questions · practice

0/6

This model set is for practice. It is not a question from any year annual examination.

1
Which of these has degree 3?
BSEB model · practice (not an annual paper)1 mark
2
The zero of p(x) = x + 5 is —
BSEB model · practice (not an annual paper)1 mark
3
(x − 5)² = x² − ______ x + 25.
BSEB model · practice (not an annual paper)1 mark
4
Before division the terms are written in descending degree.
BSEB model · practice (not an annual paper)1 mark
5
State the Factor Theorem and check x − 1 for x³ − 1.
BSEB model · practice (not an annual paper)3 marks
6
Expand (2x + 1)³. Then say how the condition x + y + z = 0 shortens Identity VIII.
BSEB model · practice (not an annual paper)5 marks
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CBSE-style questions

0/6

These are competency-based practice questions. They are not copies of a past paper.

1
A student wrote (x + 3)² = x² + 9. The missing term is —
CBSE-style · competency-based (not a PYQ)1 mark
2
p(x) = 2x² − 3x + 1 and a student finds p(1) for a zero. p(1) = 0. The conclusion is —
CBSE-style · competency-based (not a PYQ)1 mark
3

Assertion (A): x² + 5x + 6 = (x + 2)(x + 3).

Reason (R): The product of 2 and 3 is 6 and their sum is 5.

CBSE-style · competency-based (not a PYQ)1 mark
4

Assertion (A): The degree of the zero polynomial is 0.

Reason (R): A non-zero constant polynomial has degree 0.

CBSE-style · competency-based (not a PYQ)1 mark
5
Amit evaluated p(1) while dividing x³ + 1 by x + 1. The remainder came out wrong. Which value should he use, and what is the correct remainder?
CBSE-style · competency-based (not a PYQ)3 marks
6
A shop wants the square of 104 without direct multiplication. Find the value using an identity and the idea of the figure.
CBSE-style · competency-based (not a PYQ)3 marks
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Switch board with BSEB | CBSE above. The lessons follow the same NCERT chapter.

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CBSE-style · competency-based

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🧠 What you learned + equation sheet

What you learned

WhatKeep this
Degreehighest power; 0 if the constant is not zero
Zerop(c) = 0
Remainderdivision by x − a leaves p(a)
Factorp(a) = 0 means (x − a) is a factor
(a+b)²a² + 2ab + b²
Three cubesx + y + z = 0 implies x³ + y³ + z³ = 3xyz

The notes are original writing. The textbook was used only for activity order and numbers. “Verified” will be used only on a question that has a source page.