NCERT Class 8 Mathematics Mathematics: Chapter 8 — Algebraic Expressions and Identities
This chapter, "Algebraic Expressions and Identities," from NCERT Class 8 Mathematics, revisits the fundamental operations of addition and subtraction of algebraic expressions. It provides examples and methods for combining expressions by aligning like terms. The chapter also introduces the concept of multiplication of algebraic expressions, setting the stage for more complex algebraic manipulations. Understanding these operations is crucial for building a strong foundation in algebra, essential for higher mathematics and problem-solving in various CBSE curriculum contexts. The exercises provide practice in applying these rules.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 8 |
| Subject | Mathematics |
| Book | Mathematics |
| Chapter | Chapter 8 — Algebraic Expressions and Identities |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 3 minutes |
| Word count | 548 |
Learning outcomes
- Perform addition of algebraic expressions.
- Perform subtraction of algebraic expressions.
- Understand the concept of like and unlike terms.
- Recognize the additive inverse in subtraction.
- Introduce the multiplication of algebraic expressions.
Vocabulary
| Word | Meaning |
|---|---|
| Algebraic expression | A combination of variables, constants, and mathematical operations. |
| Term | A single number or variable, or numbers and variables multiplied together. |
| Like terms | Terms that have the same variables raised to the same powers. |
| Unlike terms | Terms that do not have the same variables raised to the same powers. |
| Additive inverse | The number which when added to a number gives zero. |
| Coefficient | The numerical factor of a term. |
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Practice questions
- Add the expressions: ab – bc, bc – ca, ca – ab. Answer: 0
- Subtract 5x2 – 4y2 + 6y – 3 from 7x2 – 4xy + 8y2 + 5x – 3y. Answer: 2x2 – 4xy + 12y2 + 5x – 9y + 3
- Add: 7xy + 5yz – 3zx, 4yz + 9zx – 4y, –3xz + 5x – 2xy. Answer: 5xy + 9yz + 3zx + 5x – 4y
Frequently asked questions
What are algebraic expressions?
Algebraic expressions are combinations of variables, constants, and mathematical operations like addition, subtraction, multiplication, and division.
How do you add algebraic expressions?
To add algebraic expressions, you combine like terms. Like terms have the same variables raised to the same powers.
What are like terms in algebraic expressions?
Like terms are terms that have the same variables raised to the same powers, for example, 3x² and -5x².
How do you subtract algebraic expressions?
To subtract algebraic expressions, you change the sign of each term in the expression being subtracted and then add the two expressions.
What is the additive inverse in subtraction?
The additive inverse is used in subtraction; subtracting a term is the same as adding its additive inverse (e.g., subtracting 3 is the same as adding -3).
Related resources
Important topics
Topics covered
NCERT Class 8 Mathematics — Mathematics — Chapter 8 — Algebraic Expressions and Identities. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.