Class 8 Maths – Chapter 9

Algebraic Expressions & Identities

STEP 8: Common Mistakes + Examiner View

❌ COMMON MISTAKES STUDENTS MAKE

• Mistake 1: Forgetting identities
  ❌ Writing directly without identity
  ✅ Always write identity first
• Mistake 2: Wrong sign in middle term
  ❌ (a − b)² = a² + 2ab + b² ❌
  ✅ Correct: a² − 2ab + b²
• Mistake 3: Incorrect square of terms
  ❌ (2x)² = 2x² ❌
  ✅ Correct: (2x)² = 4x²
• Mistake 4: Skipping steps
  ❌ Jumping directly to final answer
  ✅ Step-by-step earns full marks
• Mistake 5: Forgetting brackets
  ❌ x + 3² instead of (x + 3)²

👨‍🏫 EXAMINER’S VIEW (VERY IMPORTANT)

• ✔ Identity written → marks start counting
• ✔ Each correct step → step-wise marks
• ✔ Final answer without steps → marks cut
• ✔ Neat alignment → good impression
• ✔ Correct sign (+ / −) → full credit

✍️ HOW TO WRITE ANSWERS IN EXAM

1. Write the identity clearly.
2. Substitute values or expand step-by-step.
3. Keep equal (=) signs one below the other.
4. Underline final answer.

⚡ QUICK SELF-CHECK BEFORE SUBMITTING

• Did I write the identity?
• Did I square terms correctly?
• Are signs correct?
• Is the final answer boxed or underlined?