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JEE Main 202324 JanuaryMorning Shift
Exam
JEE Main
Year
2023
Date
24 January
Shift
Morning Shift
Subject
Mathematics
Chapter
Complex Number

JEE Main 2023 · 24 January · Morning Shift · Mathematics · Complex Number

Let p, q ∈ ℝ and ( 1 - 3 i ) ^ 200 = 2 ^ 199 ( p + iq ) , i = - 1 ....

Let p,q∈Rp, q \in \mathbb{R} and (1−3i)200=2199(p+iq)( 1 - \sqrt{3}i{)}^{200} = {2}^{199} ( p + iq ), i=−1i = \sqrt{- 1}. Then, p+q+q2p + q + {q}^{2} and p−q+q2p - q + {q}^{2} are roots of the equation.

Options

  1. Ax2+4x−1=0{x}^{2} + 4x - 1 = 0
  2. Bx2−4x+1=0{x}^{2} - 4x + 1 = 0
  3. Cx2+4x+1=0{x}^{2} + 4x + 1 = 0
  4. Dx2−4x−1=0{x}^{2} - 4x - 1 = 0

Correct answer

B. x2−4x+1=0{x}^{2} - 4x + 1 = 0

Step-by-step solution

Given:

(1−3i)200=2199(p+iq)( 1 - \sqrt{3}i{)}^{200} = {2}^{199} ( p + iq )

⇒(12−32i)200=12(p+iq)⇒ {\left(\dfrac{1}{2} - \dfrac{\sqrt{3}}{2}i\right)}^{200} = \dfrac{1}{2}\left(p + iq\right)

⇒(cos⁡(π3)−isin(π3))200=12(p+iq)⇒ {\left(\cos \left(\dfrac{\pi}{3}\right) - isin\left(\dfrac{\pi}{3}\right)\right)}^{200} = \dfrac{1}{2}\left(p + iq\right)

⇒(cos⁡(200π3)−isin(200π3))=12(p+iq)⇒ \left(\cos \left(\dfrac{200\pi}{3}\right) - isin\left(\dfrac{200\pi}{3}\right)\right) = \dfrac{1}{2}\left(p + iq\right)

⇒(cos⁡(201π−π3)−isin(201π−π3))=12(p+iq)⇒ \left(\cos \left(201\pi - \dfrac{\pi}{3}\right) - isin\left(201\pi - \dfrac{\pi}{3}\right)\right) = \dfrac{1}{2}\left(p + iq\right)

⇒(−cos⁡(π3)−isin(π3))=12(p+iq)⇒ \left(- \cos \left(\dfrac{\pi}{3}\right) - isin\left(\dfrac{\pi}{3}\right)\right) = \dfrac{1}{2}\left(p + iq\right)

⇒2(−12−i32)=p+iq⇒ 2\left(- \dfrac{1}{2} - i\dfrac{\sqrt{3}}{2}\right) = p + iq

⇒−1−i3=p+iq⇒ - 1 - i\sqrt{3} = p + iq

So,

p=−1,q=−3p = - 1, q = - \sqrt{3}

α=p+q+q2=2−3\alpha = p + q + {q}^{2} = 2 - \sqrt{3}

β=p−q+q2=2+3\beta = p - q + {q}^{2} = 2 + \sqrt{3}

So,

α+β=4\alpha + \beta = 4

α⋅β=1\alpha \cdot \beta = 1

Required equation is

x2−4x+1=0{x}^{2} - 4x + 1 = 0

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