Chapter 6 · Class 8 CBSE · Formula Sheet
Algebraic Expressions & Identities Formulas — Class 8 CBSE
Multiply polynomials, apply standard algebraic identities, and simplify expressions.
Key Formulas
Identity 1
(a + b)^2 = a^2 + 2ab + b^2
Identity 2
(a - b)^2 = a^2 - 2ab + b^2
Identity 3
(a + b)(a - b) = a^2 - b^2
Identity 4
(x + a)(x + b) = x^2 + (a + b)x + ab
Monomial x Monomial
3x \times 4y = 12xy
Monomial x Polynomial
a(b + c) = ab + ac
Worked Examples
1Using: Linear Equation
Solve 3x + 5 = 20.
Step 1: 3x = 20 - 5 = 15.
Step 2: x = 15 / 3 = 5.
Answer: x = 5
2Using: Algebraic Identity
Expand (a + 3)^2.
Step 1: Using (a + b)^2 = a^2 + 2ab + b^2
Step 2: = a^2 + 6a + 9.
Answer: a^2 + 6a + 9
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