Complex Numbers and Quadratic Equations
Punjab Board · Class 11 · Mathematics
Complete topic list for Complex Numbers and Quadratic Equations in Punjab Board Class 11 Mathematics. Key concepts, sub-topics, and what to focus on for board exams.
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Get startedTopics in Complex Numbers and Quadratic Equations
Introduction to Complex Numbers
- The imaginary unit i is defined as i = √(–1), so i² = –1.
- A complex number is of the form z = a + ib, where a, b ∈ ℝ.
- The real part of z = a + ib is Re(z) = a.
Powers of i – The Cyclic Pattern
- Powers of i repeat with a cycle of 4: i¹ = i, i² = –1, i³ = –i, i⁴ = 1, i⁵ = i, ...
- General rule: Divide the exponent by 4 and use the remainder to find the value.
- If remainder = 0 → i⁴ᵏ = 1
Algebra of Complex Numbers
- ADDITION: (a + ib) + (c + id) = (a+c) + i(b+d) — add real parts and imaginary parts separately.
- SUBTRACTION: (a + ib) – (c + id) = (a–c) + i(b–d) — subtract real parts and imaginary parts separately.
- MULTIPLICATION: (a + ib)(c + id) = (ac – bd) + i(ad + bc) — use distributive law and replace i² = –1.
Algebraic Identities for Complex Numbers
- All standard algebraic identities that hold for real numbers also hold for complex numbers.
- (z₁ + z₂)² = z₁² + 2z₁z₂ + z₂²
- (z₁ – z₂)² = z₁² – 2z₁z₂ + z₂²
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