Class 8 Maths – Chapter 9

Algebraic Expressions & Identities

STEP 7: Mind Map + Easy Memory Tricks

                                                

🧠 MIND MAP – Chapter at a Glance

• Algebraic Expression
  • Terms
  • Coefficient
  • Constant
• Types of Expressions
  • Monomial – 1 term (5x)
  • Binomial – 2 terms (x + 2)
  • Trinomial – 3 terms (x² + 3x − 1)
• Algebraic Identities
  • (a + b)²
  • (a − b)²
  • (a + b)(a − b)
• Uses of Identities
  • Expansion
  • Simplification
  • Finding values quickly

🟢 EASY MEMORY TRICKS (Must Remember)

• Trick 1 – PLUS Square Identity
  (a + b)²
  👉 Think: First² + Twice Product + Last²
  👉 a² + 2ab + b²
• Trick 2 – MINUS Square Identity
  (a − b)²
  👉 Same as plus, but middle term is negative
  👉 a² − 2ab + b²
• Trick 3 – Difference of Squares
  (a + b)(a − b)
  👉 Think: First² − Last²
  👉 a² − b²
• Trick 4 – Exam Shortcut
  Whenever you see brackets like (x + 3)²,
  👉 Write identity first, then substitute.

🟠 MNEMONICS (Memory Lines)

• P²T² → Plus Square = First² + Twice + Last²
• M²T² → Minus Square = First² − Twice + Last²
• FS − LS → First Square − Last Square

📝 EXAM SMART TIPS

• Write identity before expanding.
• Use brackets carefully.
• Do not skip steps – marks depend on steps.
• Practice identities daily for speed.