Class 8 · Chapter 9

Algebraic Expressions and Identities

Expansions using identities: $(a\pm b)^2$ , $(a+b)(a-b)$ , $(x+a)(x+b)$ .

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Detailed theory

(a+b)^2 = a^2 + 2ab + b^2

;

(a-b)^2 = a^2 - 2ab + b^2

;

(a+b)(a-b) = a^2 - b^2

;

(x+a)(x+b) = x^2 + (a+b)x + ab

Key concepts & formulas

(a+b)^2 = a^2 + 2ab + b^2

(a-b)^2 = a^2 - 2ab + b^2

(a+b)(a-b) = a^2 - b^2

(x+a)(x+b) = x^2 + (a+b)x + ab

Multiplication of algebraic expressions uses distributive property.