Class 8 Maths – Chapter 9

Algebraic Expressions & Identities

STEP 9: One-Page FINAL REVISION SHEET

 KEY CONCEPTS

• Algebraic Expression: Combination of variables, constants and operations.
• Term: Parts separated by + or − signs.
• Coefficient: Numerical factor of a term.
• Constant: Term without variable.

📗 TYPES OF EXPRESSIONS

• Monomial – One term (7x)
• Binomial – Two terms (x + 5)
• Trinomial – Three terms (x² + 3x − 1)

🧮 IMPORTANT ALGEBRAIC IDENTITIES

• (a + b)² = a² + 2ab + b²
• (a − b)² = a² − 2ab + b²
• (a + b)(a − b) = a² − b²

✍️ HOW TO EXPAND (EXAM METHOD)

1. Write the identity.
2. Substitute values or terms.
3. Multiply carefully.
4. Underline final answer.

⚠️ COMMON MISTAKES TO AVOID

• Wrong sign in middle term.
• Incorrect squaring of terms.
• Skipping steps.
• Forgetting brackets.

🎯 EXAM SCORING TIPS

• Always write identity first.
• Neat step-wise working gets full marks.
• Underline final answers.
• Practice identities daily for speed.