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NCERT Class 11 Maths Chapter 4 Exercise Solutions – Complex Numbers & Quadratics
z=a+bia (Re)b (Im)Argand Plane
Chapter 4 · Class XI Mathematics · NCERT Exercises

Complex Numbers & Quadratic Equations — Exercises

From i²=−1 to the Argand Plane — All 52 NCERT Solutions Explained

📂 2 Exercises 📝 28 Questions 🎓 High

Exercise Index

2 exercise files · 28 total questions

Chapter at a Glance

JEE MainJEE AdvancedCBSE BoardsBITSATKVPY
12Concepts
20Formulas
HighDifficulty
7–9%Weightage

Before You Begin

Prerequisites

  • Real number algebra
  • Quadratic equations (Class X)
  • Coordinate plane plotting

Have Ready

  • 🔧Graph paper for Argand plane
  • 🔧Powers-of-i table
  • 🔧Scientific calculator

Exercise Topic Map

Exercise 4.1Add/subtract/multiply/divide; rationalise using conjugate; |z|
Miscellaneousi^n via cycle-of-4; prove modulus identities; combined

Key Formulae

\(i^{4k}=1,\; i^{4k+1}=i,\; i^{4k+2}=-1,\; i^{4k+3}=-i\)
\(|z| = \sqrt{a^2 + b^2}\)
\(z^{-1} = \dfrac{\bar{z}}{|z|^2}\)
\(z = r(\cos\theta + i\sin\theta)\)
\(D < 0:\; \text{roots} = \dfrac{-b \pm i\sqrt{|D|}}{2a}\)

NCERT Solving Method

Step 1 — Division: multiply top and bottom by conjugate of denominator (a−bi). Step 2 — Argument: compute arctan(b/a) then adjust for quadrant using signs of a,b. Step 3 — Quadratic: compute D; if D<0 write √(−|D|)=i√|D| and proceed normally. Step 4 — Powers of i: divide exponent by 4; use the remainder.

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