Chapter 9: Algebraic Expressions and Identities
Key Identities:
• (a+b)² = a² + 2ab + b²
• (a-b)² = a² - 2ab + b²
• (a+b)(a-b) = a² - b²
Q1. Expand: (2x + 3y)².
Solution= (2x)² + 2(2x)(3y) + (3y)²
= 4x² + 12xy + 9y²
Q2. Evaluate 99 × 101 using identities.
Solution= (100-1)(100+1) = 100² - 1² = 10000 - 1 = 9999