Algebraic Expressions and Identities Class 8 Extra Questions and Answers Free PDF Download
FAQs on CBSE Important Questions for Class 8 Maths Algebraic Expressions and Identities - 2025-26
1. Why is practising important questions for CBSE Class 8 Maths Chapter 8 essential for the 2025-26 exams?
Practising important questions for Algebraic Expressions and Identities is crucial because it helps students focus on the most frequently asked topics and question patterns. This targeted practice ensures a better understanding of concepts like applying standard identities and simplifying complex expressions, which often carry significant marks in the exam. It also builds confidence and improves problem-solving speed for the 2025-26 session.
2. Which topics in Algebraic Expressions and Identities are most important for exams?
For the Class 8 Maths exam, the most important topics from this chapter that are frequently tested include:
- Multiplication of polynomials, especially a binomial by a trinomial.
- Application of the four standard identities: (a+b)², (a-b)², (a+b)(a-b), and (x+a)(x+b).
- Simplifying expressions that involve a combination of addition, subtraction, and multiplication.
- Questions that require using identities to calculate products or squares of numerical values.
3. What are the four standard algebraic identities that I must know for Class 8 Maths?
The four standard algebraic identities, as per the CBSE syllabus, are essential for solving many problems quickly. They are:
- (a + b)² = a² + 2ab + b²
- (a - b)² = a² - 2ab + b²
- (a + b)(a - b) = a² - b²
- (x + a)(x + b) = x² + (a + b)x + ab
4. How can using an algebraic identity be more efficient than direct multiplication in an exam?
Using an algebraic identity is a strategic shortcut that saves valuable time and reduces calculation errors. For example, to calculate 104 × 96, direct multiplication is slow. By representing it as (100 + 4)(100 - 4) and applying the identity (a+b)(a-b) = a² - b², the answer is found instantly as 100² - 4² = 10000 - 16 = 9984. This method is faster and less prone to mistakes under exam pressure.
5. What is a common mistake students make when subtracting algebraic expressions?
A very common error is mishandling the negative sign when subtracting one polynomial from another. For instance, in a question asking to subtract (3a - 2b) from (7a + 5b), students often forget to change the sign of every term in the expression being subtracted. The correct method is (7a + 5b) - (3a - 2b) = 7a + 5b - 3a + 2b. Forgetting to change -2b to +2b is a frequent source of incorrect answers in exams.
6. What kind of Higher-Order Thinking Skills (HOTS) questions are asked from this chapter?
HOTS questions from Algebraic Expressions and Identities often involve multiple steps or real-world applications. An expected question might be to find the area of a rectangular park whose length and breadth are given as algebraic expressions (e.g., length = 3x+4, breadth = 3x-2). This requires you to first multiply the binomials and then simplify. Another HOTS type involves using identities in reverse to find missing terms or to factorise an expression.
7. How are questions on 'multiplication of polynomials' typically framed in exams?
Questions on this topic can be framed in several ways:
- Direct Multiplication: Asking to find the product of a binomial and a trinomial, for example, (2x + 3) (x² - 4x + 5).
- Simplification: Asking to simplify a long expression involving addition, subtraction, and multiplication, which tests your ability to manage signs and combine like terms correctly.
- Verification: Asking you to multiply expressions and then verify the result by substituting a numerical value for the variable.
8. Why is it so important to correctly identify 'like terms' before adding or subtracting?
Correctly identifying and combining like terms (terms with identical variables and exponents) is the most fundamental rule in simplifying expressions. It is the mathematical equivalent of grouping similar objects before counting. If you incorrectly add unlike terms, such as adding 4x² and 7x, the entire foundation of your calculation becomes wrong. Every subsequent step will be incorrect, making this a critical skill for avoiding zero marks on complex simplification problems.
















