📚 Class IXMaths🧩 WorksheetChapter 4: Exploring Algebraic Identities
Algebraic Identities Class 9 Worksheet with Answers PDF
Class 9 Maths Algebraic Identities worksheet with answers — 75 questions with step-by-step solutions. Ganita Manjari Ch 4. Free PDF & online practice.
This free Worksheet for CBSE Class IX Maths, Chapter 4: Exploring Algebraic Identities, contains a structured worksheet with MCQs, short answer, case-based and HOTS questions in one place. It has been prepared by Sumeet Sahu at Unique Study Point, Indore, strictly following the latest NCERT syllabus for Session 2026-27.
📌 How to use this Worksheet
First revise the chapter — Exploring Algebraic Identities from your notes or textbook.
Attempt every question on your own before checking answers — this is how marks actually improve.
Mark the questions you got wrong and re-attempt them after 2–3 days.
We have 1 more resource for this chapter — see Related Materials below.
"Exploring Algebraic Identities" — Class 09
UNIQUE STUDY POINT BY SUMEET SAHU
"Exploring Algebraic Identities"
Class 09 · Maths (Ganita Manjari) · Practice Worksheet with Solutions
75 Questions
Tap any question's "Show Answer" button to reveal the full step-by-step solution.
Section A · MCQ / Assertion–Reason / True-False (Q1–Q28)
1 Mark each
1
A gardener is designing a rectangular flower bed. The length is given by (3w + 2) meters and the width by (w + 6) meters. What polynomial represents the area of the flower bed?MCQ
Simplify the rational expression a³−b³a²+ab+b², assuming that a²+ab+b² ≠ 0.MCQ
a) a² − b²
b) a − b
c) a² + b²
d) a + b
✓ Correct Answer: (b) a − b
Using a³ − b³ = (a − b)(a² + ab + b²):
a³−b³a²+ab+b² = (a−b)(a²+ab+b²)a²+ab+b² = a − b (cancelling the common non-zero factor).
21
Statement I: [(a²−b²)³+(b²−c²)³+(c²−a²)³] ÷ [(a+b)³+(b+c)³+(c+a)³] = (a+c)(c+a). Statement II: a²+b²+c² − ab − bc − ca = ½[(a−b)²+(b−c)²+(c−a)²]Statement-Based
a) Both Statement-I and Statement-II are true.
b) Statement-I is true but Statement-II is false.
c) Statement-I is false but Statement-II is true.
d) Both Statement-I and Statement-II are false.
✓ Correct Answer: (c) Statement-I is false but Statement-II is true.
Statement I: Since (a²−b²)+(b²−c²)+(c²−a²) = 0, we get (a²−b²)³+(b²−c²)³+(c²−a²)³ = 3(a²−b²)(b²−c²)(c²−a²), and similarly the denominator = 3(a+b)(b+c)(c+a).
The ratio simplifies to (a−b)(a+c)(b−a) … which is not equal to (a+c)(c+a) in general — so Statement I is false.
Statement II: ½[(a−b)²+(b−c)²+(c−a)²] = ½[2a²+2b²+2c²−2ab−2bc−2ca] = a²+b²+c²−ab−bc−ca. This is a standard true identity, so Statement II is true.
22
Assertion (A): To simplify (2p − 3q + 4r)², one must first expand (2p − 3q)² and then treat 4r as a separate term applying (A + B)² form. Reason (R): The algebraic identity (x + y + z)² = x² + y² + z² + 2xy + 2yz + 2zx requires all terms x, y, z to be positive.Assertion-Reason
a) Both A and R are true, and R is the correct explanation of A
b) Both A and R are true, but R is not the correct explanation of A
c) A is true, but R is false
d) A is false, but R is true
✓ Correct Answer: (c) A is true, but R is false
Assertion: Grouping (2p−3q) as one term and 4r as another, then applying (A+B)² twice, is indeed a valid way to expand the trinomial square — so A is true.
Reason: The identity (x+y+z)² = x²+y²+z²+2xy+2yz+2zx holds for any real x, y, z, including negative ones (signs are simply carried into the variables) — so R is false.
23
Assertion (A): The expression (K + L − M)² will have three negative terms in its expansion using the general identity for three terms. Reason (R): The square of a negative term is always positive, but the product of a positive and a negative term is negative.Assertion-Reason
a) Both A and R are true and R is the correct explanation of A.
b) Both A and R are true but R is not the correct explanation of A.
c) A is true but R is false.
d) A is false but R is true.
✓ Correct Answer: (d) A is false but R is true.
Assertion: (K+L−M)² = K²+L²+M²+2KL−2LM−2KM, which has only two negative terms (−2LM and −2KM), not three — so A is false.
Reason: The square of any real number is non-negative, and a positive × negative product is indeed negative — this statement is true in general.
24
Assertion (A): Factorisation of x³ − 27 is (x − 3)(x² + 3x + 9). Reason (R): a³ − b³ = (a − b)(a² + ab + b²).Assertion-Reason
a) Both A and R are true, and R is the correct explanation of A
b) Both A and R are true, but R is not the correct explanation of A
c) A is true, but R is false
d) A is false, but R is true
✓ Correct Answer: (a) Both A and R are true, and R is the correct explanation of A
Reason: a³−b³=(a−b)(a²+ab+b²) is a standard true identity.
Assertion: x³ − 27 = x³ − 3³ = (x−3)(x²+3x+3²) = (x−3)(x²+3x+9) — true, and it follows directly by applying Reason’s identity.
25
Assertion (A): The equation x² − 4 = (x − 2)(x + 2) is an algebraic identity. Reason (R): This equation is true for all real values of x, as expanding the right side yields x² − 4.Assertion-Reason
a) Both A and R are true, and R is the correct explanation of A
b) Both A and R are true, but R is not the correct explanation of A
c) A is true, but R is false
d) A is false, but R is true
✓ Correct Answer: (a) Both A and R are true, and R is the correct explanation of A
An algebraic identity is an equality that holds for all values of the variable.
Expanding: (x−2)(x+2) = x(x+2) − 2(x+2) = x²+2x−2x−4 = x²−4, true for every real x.
So Assertion is true, and Reason correctly explains it.
26
Assertion (A): An algebraic identity is a type of equation that holds true for all possible real values of its variables. Reason (R): The equation (x − y)² = x² − y² is an example of an algebraic identity.Assertion-Reason
a) Both A and R are true, and R is the correct explanation of A
b) Both A and R are true, but R is not the correct explanation of A
c) A is true, but R is false
d) A is false, but R is true
✓ Correct Answer: (c) A is true, but R is false
Assertion correctly defines an algebraic identity — true.
Reason: (x−y)² = x² − 2xy + y², which is not the same as x²−y² in general. E.g. x=1, y=2: (1−2)²=1 but 1²−2²=−3. So R is false.
27
State whether the given statement is True or False: (a) The degree of the polynomial g(x) = (p − x)³ + 14 is 3.
Expanding (p − x)³ gives a term in −x³, so the highest power of x in g(x) is 3.
Adding the constant 14 does not change the highest power.
So the degree of g(x) is indeed 3 — the statement is True.
✓ (a) True
28
Fill in the blanks: (a) The value of 5.63 × 5.63 + 11.26 × 2.37 + 2.37 × 2.37 is ________.
Notice 11.26 = 2 × 5.63, so the expression is 5.63² + 2(5.63)(2.37) + 2.37².
This matches the identity a² + 2ab + b² = (a + b)² with a = 5.63, b = 2.37.
= (5.63 + 2.37)² = (8)² = 64.
✓ (a) 64
Section B · Match & Short Answer (Q29–Q45)
2 Marks each
29
If x + y = 9 and xy = 20, then find the value of x² + y².
(ii) Rewrite as 1 − 2(a+b) − 3(a+b)². Let t = (a+b): = 1 − 2t − 3t² = 1 − 3t + t − 3t² = (1−3t) + t(1−3t) = (1+t)(1−3t).
Substitute back: = (1 + a + b)[1 − 3(a+b)] = (1 + a + b)(1 − 3a − 3b).
✓ (i) (2a − 5)(2a − 1); (ii) (1 + a + b)(1 − 3a − 3b)
55
Try to evaluate the following using a suitable identity: i. 35² ii. 65² iii. 85² iv. 105². Do you observe any interesting pattern?
Use (a + b)² = a² + 2ab + b².
i. 35² = (30+5)² = 900 + 300 + 25 = 1225.
ii. 65² = (60+5)² = 3600 + 600 + 25 = 4225.
iii. 85² = (80+5)² = 6400 + 800 + 25 = 7225.
iv. 105² = (100+5)² = 10000 + 1000 + 25 = 11025.
Pattern: every number here ends in 5, and its square always ends in 25 — the digits before the 25 come from multiplying the number before the 5 with the next whole number (e.g. 3×4=12 for 35², 6×7=42 for 65²).
✓ 35²=1225, 65²=4225, 85²=7225, 105²=11025
56
Factorise: x² + [a²+1a]x + 1
Split the middle term: x² + ax + 1ax + 1 = x² + ax + xa + 1.
(ii) a²(b+c) − (b+c)³ = (b+c)[a² − (b+c)²] = (b+c)(a+b+c)(a−b−c), using a²−b²=(a−b)(a+b).
✓ (i) 2(x−2)(x+2)(x²+4); (ii) (b+c)(a+b+c)(a−b−c)
Section D · Case Study Based (Q61–Q65)
4 Marks each
61
Case Study: A municipal corporation is redesigning a square-shaped city park that currently measures 100 m × 100 m. To improve functionality, they decide to expand the park by adding 5 m to both the length and the width, making it a larger square (105 m × 105 m). Later, to build a footpath around it, they take 2 m off the length and 2 m off the width of this expanded park, making it (105−2) m × (105−2) m.
Which algebraic identity is most useful to calculate the area of the initially expanded park (105 m × 105 m)? (1)
What is the exact area of the expanded park (105 m × 105 m) using identities? (1)
If the park dimensions become (105−2) × (105−2), find its area using a suitable identity. (2) OR — Find the total area of the footpath built around the park (the difference between the expanded park area and the final park area). (2)
(i) Since 105 = 100 + 5, the side length has the form (a + b) with a = 100, b = 5. The most useful identity is (a + b)² = a² + 2ab + b².
(ii) (100 + 5)² = 100² + 2(100)(5) + 5² = 10000 + 1000 + 25 = 11025 m².
(iii) New side = 105 − 2 = 103 m, so area = (105 − 2)². Use (a − b)² = a² − 2ab + b² with a = 105, b = 2:
✓ Identity: (a±b)²; Expanded park area = 11025 m²; Final park area = 10609 m² (footpath area = 416 m²)
62
Case Study: A carpenter is building a cube-shaped wooden gift box. The volume of the box, in cubic centimetres, works out to 8y³ + 36y² + 54y + 27, where y is a design parameter he uses across different box sizes.
Express this volume in the form (a + b)³ by identifying a and b. (1)
Write down the side length of the cube in terms of y. (1)
If y = 3 cm, find the actual side length and the volume of the box. (2) OR — If the volume were instead 8y³ − 36y² + 54y − 27, what would the side length be, and why does the sign pattern in the expression change? (2)
(i) Comparing the first and last terms: 8y³ = (2y)³ so a = 2y; 27 = 3³ so b = 3.
(ii) Since volume = (side)³, side length = (2y + 3) cm.
(iii) At y = 3: side = 2(3)+3 = 9 cm. Volume = 9³ = 729 cm³.
OR: The expression 8y³−36y²+54y−27 matches (a−b)³ = a³−3a²b+3ab²−b³, so the side length would be (2y − 3) cm. The signs alternate ( +, −, +, − ) because substituting −b into the odd-power terms of the expansion keeps flipping their sign.
✓ Volume = (2y+3)³; Side = (2y+3) cm; at y=3: side = 9 cm, volume = 729 cm³
63
Case Study: National Association For The Blind (NAB) aims to empower and well-inform the visually challenged population of our country, enabling them to lead a life of dignity and productivity. Ravi donated ₹(x³ + 1x³) to NAB. When his cousin asked him the amount donated, he just gave the hint: x + 1x = 10.
When (x + a)(x + b) is expanded, what is the resulting expression in the form (x² + ______ x + ab)? (1)
What is the mathematical formula for the identity represented as (x − y)³? (1)
What is the amount donated by Ravi? (2) OR — What is the amount donated by Ravi if x + 1x = 7? (2)
(i) (x + a)(x + b) = x² + (a + b)x + ab — the blank is filled by (a + b).
OR: With x + 1x = 7: (x³ + 1x³) + 3(7) = 343 ⇒ x³ + 1x³ = 343 − 21 = 322. So Ravi would have donated ₹322.
✓ (i) (a+b); (ii) (x−y)³=x³−y³−3xy(x−y); (iii) ₹970 (or ₹322 if x + 1x = 7)
64
Case Study: A housing society's square pool deck currently measures 50 m × 50 m. To create more lounging space, the committee decides to add 6 m to both the length and the width, making it a larger square (56 m × 56 m). Later, to lay a tiled walking border around this enlarged deck, they take 4 m off the length and 4 m off the width.
Which identity is most useful to calculate the area of the enlarged deck (56 m × 56 m)? (1)
Find the exact area of the enlarged deck using that identity. (1)
After the border is cut in, the deck becomes (56−4) m on each side. Find its new area using a suitable identity. (2) OR — Find the difference between the area of the enlarged deck and the final deck. (2)
(i) Since 56 = 50 + 6, the area is (50 + 6)²; the useful identity is (a + b)² = a² + 2ab + b².
(ii) (50+6)² = 50² + 2(50)(6) + 6² = 2500 + 600 + 36 = 3136 m².
(iii) New side = 56 − 4 = 52 m, area = (56−4)². Use (a−b)² = a²−2ab+b² with a=56, b=4:
OR: Difference = 3136 − 2704 = 432 m² (also checks out directly: 52 × 52 = 2704 m²).
✓ Enlarged deck area = 3136 m²; Final deck area = 2704 m² (difference = 432 m²)
65
Case Study: A school garden committee decided to redesign a square flower bed of side x metres by adding a border of uniform width 3 metres on two adjacent sides. This forms a larger square plot of side (x + 3) metres, and its area can be expressed using the identity (a + b)² = a² + 2ab + b². The original square had side 7 metres.
Using the identity (a + b)² = a² + 2ab + b², expand (x + 3)² and find the total area of the new plot when x = 7. (1)
If instead the border width is b metres and x = 10, what is the value of 2xb when the total area of the new plot equals 196 m²? (Use the expansion of (x + b)².) (1)
A rectangular section of the plot is separated for roses. Its area is given by x² + 10x + 25 m². Factorise this expression completely and state the side length of this square rose section. (2) OR — Another section has area 4x² + 12x + 9 m². Factorise completely and find the perimeter of this square section in terms of x. (2)