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JEE Main 20241 FebruaryMorning Shift
Exam
JEE Main
Year
2024
Date
1 February
Shift
Morning Shift
Subject
Mathematics
Chapter
Complex Number

JEE Main 2024 · 1 February · Morning Shift · Mathematics · Complex Number

Let P = \ z ∈ ℂ: |z + 2 - 3i| ≤ 1\ and Q = \ z ∈ ℂ: z(1 + i) + ¯ z...

Let P={z∈C:∣z+2−3i∣≤1}P = \left\{z \in \mathbb{C}: \left|z + 2 - 3i\right| \le 1\right\} and Q={z∈C:z(1+i)+z¯(1−i)≤−8}Q = \left\{z \in \mathbb{C}: z\left(1 + i\right) + \overset{¯}{z}\left(1 - i\right) \le - 8\right\}. Let in P∩Q,∣z−3+2i∣P \cap Q, \left|z - 3 + 2i\right| be maximum and minimum at z1{z}_{1} and z2{z}_{2} respectively. If ∣z1∣2+2∣z∣2=α+β2,{\left|{z}_{1}\right|}^{2} + 2{\left|z\right|}^{2} = \alpha + \beta\sqrt{2}, where α,β\alpha, \beta are integers, then α+β\alpha + \beta equals __________Let P = \ z ∈ ℂ: |z + 2 - 3i| ≤ 1\ and Q = \ z ∈ ℂ: z(1 + i) + ¯ z (1 - i) ≤ - 8\ . Let in P Q, |z - 3 + 2i| be maximum

Correct answer

0

Step-by-step solution

Given: ∣z+2−3i∣≤1\left|z + 2 - 3i\right| \le 1

Putting, z=x+iyz = x + iy.

⇒(x+2)2+(y−3)2≤1...(i)⇒ {\left(x + 2\right)}^{2} + {\left(y - 3\right)}^{2} \le 1 . . . \left(i\right)

For the circle represented in equation \left(i\right),centreis (−2,3) andradius,, centre is \left(- 2, 3\right) and radius,r = 1.</p><p>Itisgiventhat,.</p><p>It is given that,z\left(1 + i\right) + z \left(1 - i\right) \le - 8</p><p></p><p>⇒ \left(x + iy\right)\left(1 + i\right) + \left(x - iy\right)\left(1 - i\right) \le - 8</p><p></p><p>⇒ x + ix - y + iy + x - ix - iy - y \le - 8</p><p></p><p>⇒ 2x - 2y \le - 8</p><p></p><p>⇒ x - y + 4 = 0</p><p>So,thelinepassingthrough (3,−2) andperpendicularto</p><p>So, the line passing through \left(3, - 2\right) and perpendicular tox - y + 4 = 0isgivenby,is given by,x + y - 1 = 0.</p><p><imgalt=""src="https://cdn−question−pool.getmarks.app/pyq/jeemain/6a48608a−82e8−4389−92ee−b95c00c27545.png"style="width:350px;height:272px;"/></p><p>So,thedistanceofline.</p><p><img alt="" src="https://cdn-question-pool.Quantrex.app/pyq/jee_main/6a48608a-82e8-4389-92ee-b95c00c27545.png" style="width: 350px; height: 272px;"/></p><p>So, the distance of linex - y + 4 = 0fromthecentre (−2,3)from the centre \left(- 2, 3\right) is given by,

d=∣−2−3+42∣d = \left|\dfrac{- 2 - 3 + 4}{\sqrt{2}}\right|

⇒d=12⇒ d = \dfrac{1}{\sqrt{2}}

Now, x+y−1=0x + y - 1 = 0 can be rewritten as,

x+2−12=y−312=CAorCB\dfrac{x + 2}{\dfrac{- 1}{\sqrt{2}}} = \dfrac{y - 3}{\dfrac{1}{\sqrt{2}}} = CA\text{or}CB

For CA=−12CA = \dfrac{- 1}{\sqrt{2}} and CB=1CB = 1, A≡(−32,52)A ≡ \left(\dfrac{- 3}{2}, \dfrac{5}{2}\right) and B≡(−12−2,12+3)B ≡ \left(\dfrac{- 1}{\sqrt{2}} - 2, \dfrac{1}{\sqrt{2}} + 3\right).

⇒∣z1∣2=(2+12)2+(3+12)2⇒ {\left|{z}_{1}\right|}^{2} = {\left(2 + \dfrac{1}{\sqrt{2}}\right)}^{2} + {\left(3 + \dfrac{1}{\sqrt{2}}\right)}^{2}

⇒∣z1∣2=4+12+22+9+12+32⇒ {\left|{z}_{1}\right|}^{2} = 4 + \dfrac{1}{2} + 2\sqrt{2} + 9 + \dfrac{1}{2} + 3\sqrt{2}

⇒∣z1∣2=14+52⇒ {\left|{z}_{1}\right|}^{2} = 14 + 5\sqrt{2}

⇒∣z2∣2=2(94+254)⇒ {\left|{z}_{2}\right|}^{2} = 2\left(\dfrac{9}{4} + \dfrac{25}{4}\right)

⇒∣z2∣2=17⇒ {\left|{z}_{2}\right|}^{2} = 17

⇒∣z1∣2+2∣z2∣2=31+52⇒ {\left|{z}_{1}\right|}^{2} + 2{\left|{z}_{2}\right|}^{2} = 31 + 5\sqrt{2}

⇒α=31,β=5⇒ \alpha = 31, \beta = 5

⇒α+β=36⇒ \alpha + \beta = 36

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