Quadratic Formula: x = (−b ± √(b²−4ac)) / 2a
Discriminant Δ = b²−4ac: Δ>0 → 2 roots · Δ=0 → 1 root · Δ<0 → none
Vieta's formulas (ax²+bx+c=0): α+β = −b/a · αβ = c/a
Sum of AP: Sₙ = n/2·(2a + (n−1)d) · nth term: aₙ = a + (n−1)d
GP nth term: aₙ = ar^(n−1) · Sum: Sₙ = a(rⁿ−1)/(r−1)
Laws of Exponents: aᵐ·aⁿ=aᵐ⁺ⁿ · (aᵐ)ⁿ=aᵐⁿ · a^(p/q) = ᵠ√(aᵖ)
- Vertex of parabola: x = −b/2a
- α² + β² = (α+β)² − 2αβ (key identity)
- nth term from Sₙ: aₙ = Sₙ − Sₙ₋₁ (for n ≥ 2)