Algebraic Identities
Learn standard identities and expand expressions quickly and accurately.
Master algebra through visual learning, Algebra Tiles, factorisation techniques, rational expressions, and complete Class 9 Maths Chapter 4 Solutions designed to make every concept simple, logical, and easy to remember.

Everything you need to master Exploring Algebraic Identities is organised here. Learn the concepts first, practise them through NCERT exercises, and finish with a quick revision before your exam.
Follow this guided learning path to build your understanding step by step—from recognising patterns to confidently solving every NCERT question.
Explore every part of Chapter 4 in one simple, guided learning path.
Don’t memorise formulas first. Understand the ideas behind them and every identity will become easier to remember and apply.
Algebraic Identities are mathematical patterns that always work. Once you understand them, you can expand expressions, factorise them, perform quick calculations and simplify rational expressions with confidence.
Before solving Exercise 4.1, understand these six important ideas.
Every identity begins with a repeating mathematical pattern. If the pattern is always true, it becomes an identity.
An identity is true for every value of the variables, while an equation is true only for specific value(s).
Squares and rectangles show exactly where every term comes from. Understanding the picture makes the identity easy.
Expansion opens brackets. Factorisation closes them again. They are simply opposite directions of the same algebraic identity.
One identity helps you expand expressions, factorise quickly, perform smart calculations and simplify rational expressions.
Exercise 4.1 introduces identities. Later exercises use the same identities for factorisation, Algebra Tiles and rational expressions.
Every algebraic identity is built on a simple mathematical pattern. If you understand the pattern, you can expand, factorise and simplify expressions without memorising every formula separately.
Don’t ask “Which formula should I memorise?”
Ask “Which pattern do I recognise?”
All 11 NCERT Algebraic Identities in one place. Perfect for quick revision before solving questions or revising for exams.
This Formula Wall is designed for fast revision. Learn the detailed concepts inside the exercise pages, then return here whenever you need a quick formula recap.
Discover how squares, rectangles, and cubes transform into algebraic identities. See the picture. Understand the formula.
Build Shapes. Discover Algebra.
Explore how NCERT Class 9 Maths Chapter 4 – Exploring Algebraic Identities uses Algebra Tiles to make multiplication, factorisation and algebraic identities easy to understand. Instead of memorising formulas, you’ll build expressions with simple shapes and discover the answer yourself.
Don’t Guess the Method. Ask the Right Question.
Every algebraic expression can be factorised, but the first step is choosing the correct method. This simple decision guide for Class 9 Maths Chapter 4 – Exploring Algebraic Identities helps you decide whether to use the Common Factor, Grouping, Split the Middle Term, or an Algebraic Identity.
Understand the Concept Before You Solve the Exercises.
Master the Class 9 Maths Chapter 4 Solutions through these Think & Reflect Solutions based on the latest NCERT Ganita Manjari (2026). Each solution is explained step by step to help you understand Exploring Algebraic Identities, Algebra Tiles, Factorisation and Rational Expressions before solving the NCERT exercises with confidence.
On the previous page, we observed a surprising pattern for three consecutive square numbers.
In both examples, we added the smallest and largest square numbers and then subtracted twice the middle square(s). The result was always the same. Now NCERT asks us to investigate whether a similar pattern exists for four consecutive square numbers.
Try and find other patterns like this one. For example, you could consider 4 consecutive squares and see if you can find a pattern.
Instead of guessing the answer directly, let us try one example and carefully observe what happens.
Take four consecutive square numbers:
Now add the first and last square numbers.
Also add the two middle square numbers.
Now compare these two sums.
Try another set of four consecutive squares:
Again, we get the same answer.
For these examples, we observe the pattern:
So, for four consecutive square numbers, the difference between the sum of the first and last squares and the sum of the two middle squares is always 4.
To answer all four questions, first recall the algebraic identity
Now compare this with
Notice that the only extra term is 2ab. Therefore, the comparison depends only on whether 2ab is positive, negative or zero.
This is possible only when a and b have opposite signs.
This happens when a and b have the same sign (both positive or both negative).
This is possible only when a = 0 or b = 0.
The deciding term is
If 2ab is positive, then (a+b)2 is larger. If 2ab is negative, then a2+b2 is larger. If 2ab = 0, both expressions are equal.
| Condition | Conclusion |
|---|---|
| ab < 0 | a and b have opposite signs, so (a+b)2 < a2 + b2 |
| ab > 0 | a and b have the same sign, so (a+b)2 > a2 + b2 |
| ab = 0 | Either a = 0 or b = 0, so (a+b)2 = a2 + b2 |
| Deciding Term | The comparison depends only on the term 2ab. |
We already know the identity
Now replace b by −b everywhere.
Now simplify each term.
Only the middle term changes its sign because replacing b by −b makes 2ab → −2ab, while (−b)² = b² remains positive.
Label the squares and rectangles in Fig. 4.4 so that it represents the identity
The large square has side (a + b + c), so its total area is (a + b + c)². Divide this square into smaller squares and rectangles as shown below.
The figure contains a², b², c², two rectangles of area ab, two rectangles of area bc, and two rectangles of area ac. Therefore, the total area of the large square is
Try to evaluate the following using a suitable identity:
Do you observe any interesting pattern?
Notice that every number ends with 5. Therefore, we can use the identity
Here, take b = 5.
| Number | Square |
|---|---|
| 35² | 1225 |
| 65² | 4225 |
| 85² | 7225 |
| 105² | 11025 |
All these numbers end with 5, and their squares always end with 25. This pattern helps us calculate such squares quickly using the identity (a + b)².
Observe the two rows of figures below. They represent an algebraic identity. Try to identify the identity.
Instead of guessing the algebraic identity, we shall prove it using the areas of different coloured parts of the figure.
In the next step, we shall begin by finding the dimensions and area of Rectangle R₁.
Before finding the area of Rectangle R1, we must first determine its length and breadth from the given figure.
The total length of the upper side of the large square is
The white square occupies a length of
Therefore, the remaining horizontal length gives the width of Rectangle R1.
Now observe the left side of the large square. The total height of the square is
The green square occupies a height of
Therefore, the remaining vertical length gives the height of Rectangle R1.
We have now found both the dimensions of Rectangle R1. In the next step, we shall use these dimensions to calculate its area.
Now we know both the dimensions of Rectangle R1.
We know that,
Substituting the dimensions of Rectangle R1,
We have successfully found the dimensions and area of Rectangle R1. Next, we shall calculate the dimensions and area of Rectangle R2 in the same way.
Now let us find the dimensions of Rectangle R2. We shall begin by finding its horizontal side.
The total length of the upper side of the large square is
The green square occupies a length of
Therefore, the remaining horizontal length gives the horizontal side of Rectangle R2.
Now observe the right side of the large square. The total height of the square is
The white square occupies a height of
Therefore, the remaining vertical length gives the vertical side of Rectangle R2.
We have now found both the dimensions of Rectangle R2:
Horizontal Side = a − b + c
Vertical Side = a + b − c
In the next step, we shall use these dimensions to calculate the area of Rectangle R2.
Now we know both the dimensions of Rectangle R2.
We know that,
Substituting the dimensions of Rectangle R2,
We have now found the areas of both Rectangle R1 and Rectangle R2. In the next step, we shall find the common overlapping region, which has been counted in both rectangles.
The two rectangles R₁ and R₂ overlap each other. To find the area of this common region, we must first determine its side length.
The horizontal side of Rectangle R₂ is
Out of this length, the white square occupies
Therefore,
Now let us find the vertical side of the common overlapping region. The vertical side of Rectangle R₁ is
Out of this length, the green square occupies
Therefore,
The horizontal side and the vertical side of the common region are both equal to
Since both sides are equal, the common overlapping region is a square. Therefore, its area is
Now let us calculate the areas of the remaining two squares shown in the figure.
The side of the green square is
Area of a square = Side × Side
The side of the white square is
Area of a square = Side × Side
The side of the complete outer square is
Therefore,
The same figure can also be obtained by combining:
Expanding and simplifying the area equation step by step:
🎉 We have successfully proved this identity by comparing the area of the complete square with the areas of its different parts.
In the next step, we will rearrange the algebra tiles by splitting 7x = 2x + 5x and observe whether a new rectangle can be formed.
In the previous arrangement, the 7x tiles were divided into 3x and 4x. Now, split them differently as
Arrange the tiles again so that they form a complete rectangle without leaving any gaps.
Observe the new arrangement carefully. In the next step, we will identify the length and breadth of the rectangle formed.
From the new arrangement of algebra tiles, observe the sides of the rectangle carefully.
Since the figure is a rectangle, its area is equal to
In the next step, we shall expand (x + 2)(x + 5) and compare the result with the original polynomial.
The dimensions of the rectangle are (x + 2) and (x + 5). Therefore,
Now compare this result with the previous arrangement.
| Split of 7x | Rectangle | Polynomial |
|---|---|---|
| 3x + 4x | (x + 3)(x + 4) | x² + 7x + 12 |
| 2x + 5x | (x + 2)(x + 5) | x² + 7x + 10 |
Yes, a similar rectangular arrangement can be formed by splitting 7x = 2x + 5x. However, the rectangle now represents the polynomial x² + 7x + 10, which is different from the previous polynomial x² + 7x + 12. Hence, different ways of splitting the middle term can produce different rectangular arrangements and different polynomials.
In this activity, we will use Algebra Tiles to understand how multiplication and factorisation work visually. Instead of memorising formulas, we will arrange tiles to form complete rectangles and discover the answers ourselves.
We will first solve Part (i) by arranging the Algebra Tiles for (x + 2) and (x + 3). As the rectangle is formed, the product will appear automatically.
We shall represent both expressions using Algebra Tiles and then arrange them into one complete rectangle.
The first factor (x + 2) contains
The second factor (x + 3) contains
Arrange all the Algebra Tiles to form one complete rectangle.
The completed rectangle clearly shows how multiplication takes place visually.
After arranging the rectangle, we observe:
Instead of multiplying term by term, Algebra Tiles allow us to see the product visually. Once the rectangle is complete, the total area automatically gives the expanded algebraic expression.
Represent this expression using Algebra Tiles and arrange them into one complete rectangle.
Therefore, the required factors are (x + 5) and (x + 6).
When Algebra Tiles form one complete rectangle, the length and width of the rectangle directly give the factors of the algebraic expression. This visual method makes factorisation easy to understand without memorising rules.
We have seen that
Generalise the above pattern to obtain an expression for (x + a)(x + b).
Observe the two given examples carefully.
| Expression | Expanded Form |
|---|---|
| (x+3)(x+4) | x²+7x+12 |
| (x+6)(x+7) | x²+13x+42 |
From these examples we observe that:
Now replace the numbers by two general numbers a and b.
Hence, for every expression of the form (x+a)(x+b), the coefficient of x is always (a+b), and the constant term is always ab.
Coefficient of x = a+b
Constant Term = ab
James and Reshma are simplifying the algebraic expression
James first expands (a − b)², whereas Reshma first uses the identity (a-b)(a+b)=a²−b². Determine whether both students are correct.
Let us verify both methods one by one.
James first uses the identity
Substituting this into the given expression,
Reshma groups one factor of (a-b) and first applies the identity
Therefore,
Both methods give exactly the same simplified expression. This happens because both students used valid algebraic identities correctly. Although the order of applying the identities is different, the final result remains the same.
Both James and Reshma are correct. They used different algebraic identities, but both methods simplify the expression correctly.
We already know that
We have also verified that
Observe that (x−y) is a common factor in both identities.
Do you think (x−y) is also a factor of
x⁴−y⁴?
Can you predict whether it is also a factor of
x⁵−y⁵?
Instead of solving immediately, let us first compare the two identities.
| Identity | Factorised Form |
|---|---|
| x² − y² | (x−y)(x+y) |
| x³ − y³ | (x−y)(x²+xy+y²) |
Now compare the two factorised forms.
Did the first factor change? No. Only the second factor changed. This is the important pattern that NCERT wants us to observe.
Since x²−y² contains (x−y) and x³−y³ also contains (x−y), what do you think about x⁴−y⁴?
Before reading further, pause for a moment and make your own prediction. Do you think (x−y) will again be a common factor?
To check whether our prediction is correct, let us factorise x⁴ − y⁴.
Notice that x⁴ and y⁴ are perfect squares. So, we can write
Now apply the identity
We get
But we already know that
Substituting this result,
✅ Our prediction was correct.
The expression
x⁴ − y⁴
also contains the common factor
(x − y).
Now compare all three identities.
| Expression | Common Factor |
|---|---|
| x² − y² | (x − y) |
| x³ − y³ | (x − y) |
| x⁴ − y⁴ | (x − y) |
What do you think about x⁵ − y⁵? Will it also contain the factor (x − y)? Take a moment to think before reading the answer.
In the next step, we will verify our prediction and then discover a beautiful new algebraic identity involving three variables.
If the same pattern continues, then x⁵ − y⁵ should also contain the common factor (x−y). Let us verify it.
Our prediction is correct. The factor (x−y) appears once again.
From all four identities, we notice one beautiful mathematical pattern.
| Expression | Common Factor |
|---|---|
| x²−y² | (x−y) |
| x³−y³ | (x−y) |
| x⁴−y⁴ | (x−y) |
| x⁵−y⁵ | (x−y) |
Whenever you see an expression of the form xⁿ−yⁿ, always check whether (x−y) is a common factor. This simple observation helps us factorise many algebraic expressions.
So far, we have explored identities involving two variables. Now NCERT introduces a new identity involving three variables. Instead of guessing, let us verify it by multiplying the two expressions step by step.
NCERT now introduces a beautiful identity involving three variables. Our goal is to check whether multiplying the following two expressions really gives the required result.
To verify this identity, multiply each term of (x+y+z) with every term of the second bracket.
After multiplying, several positive and negative terms cancel each other. Only four terms remain.
Hence, the identity is verified.
Identity Verified
Simplify the following rational expression.
Hint: Start by factorising the denominator t² + 2ts − 48s².
Whenever we simplify a rational expression, we should first factorise the denominator and the numerator. Since NCERT has already given us a hint, let us begin with the denominator.
We have
Find two numbers whose
The required numbers are 8 and −6.
✅ The denominator has now been factorised.
Now look carefully at the numerator.
Can you recognise it as a familiar algebraic identity? Try rewriting it in descending powers of t before moving to the next step.
To recognise the algebraic identity more easily, rewrite the numerator in descending powers of t.
Now compare it with the identity
Here, a=t and b=6s. Therefore,
✅ Now both the numerator and denominator have been factorised.
Replace the numerator and denominator with their factorised forms.
The factor (t−6s) appears in both the numerator and the denominator. So, we can cancel one common factor.
To simplify any rational expression, always remember these four steps:
Find quick answers related to Class 9 Maths Chapter 4 Solutions, algebraic identities, factorisation, Algebra Tiles and rational expressions based on the latest NCERT Ganita Manjari (2026).
Algebraic identities are equations that are true for every value of the variables. They help simplify expressions, perform faster calculations and solve factorisation problems.
An algebraic expression is a combination of variables, constants and operations, whereas an algebraic identity is an equation that remains true for all permissible values of the variables.
The identities (a+b)², (a−b)², a²−b², (x+a)(x+b), x³−y³ and x³+y³+z³−3xyz are the most important identities used throughout Chapter 4.
Algebra Tiles are visual models that help students understand multiplication, factorisation and algebraic identities by representing algebraic expressions using geometric tiles.
Start by checking for a common factor. If none exists, try grouping, splitting the middle term or using a suitable algebraic identity. The correct method depends on the form of the expression.
A rational expression is a fraction whose numerator and denominator are algebraic expressions. To simplify it correctly, first factorise both parts and then cancel only the common factors.
No. Individual terms cannot be cancelled. Only common factors can be cancelled after completely factorising both the numerator and the denominator.
Yes. All Class 9 Maths Chapter 4 Solutions on Maths Gurukulam are prepared according to the latest NCERT Ganita Manjari (2026) textbook and follow the current CBSE guidelines with simple, step-by-step explanations.
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These Class 9 Maths Chapter 4 Solutions for Exploring Algebraic Identities have been carefully prepared according to the latest NCERT Ganita Manjari (2026) and the current CBSE curriculum. Every solution is explained in a simple, step-by-step teaching style to help students understand Algebraic Identities, Factorisation, Algebra Tiles and Rational Expressions. The goal is to build strong concepts, improve problem-solving skills and help students perform confidently in school and CBSE examinations.
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