Class 8 Maths – Chapter 9

Algebraic Expressions & Identities

STEP 2: NCERT Questions & Answers

Q1. Identify the terms, coefficients and variables in the expression: 3x² − 5x + 7

Answer:

• Terms: 3x², −5x, 7
• Variable: x
• Coefficient of x² = 3
• Coefficient of x = −5
• Constant term = 7

Q2. Classify the following as monomial, binomial or trinomial:

(a) 5x (b) x + 4 (c) x² + 3x + 2

Answer:

• (a) 5x → Monomial
• (b) x + 4 → Binomial
• (c) x² + 3x + 2 → Trinomial

Q3. Add: (3x + 5) and (2x − 1)

Answer:

(3x + 5) + (2x − 1)
= 3x + 2x + 5 − 1
= 5x + 4

Q4. Subtract (2x − 3) from (5x + 4)

Answer:

(5x + 4) − (2x − 3)
= 5x + 4 − 2x + 3
= 3x + 7

Q5. Using identity, find (x + 3)²

Answer:

(x + 3)² = x² + 2×x×3 + 3²
= x² + 6x + 9

Q6. Find (a − b)(a + b)

Answer:

(a − b)(a + b) = a² − b²