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JEE Main 202126 FebruaryEvening Shift
Exam
JEE Main
Year
2021
Date
26 February
Shift
Evening Shift
Subject
Mathematics
Chapter
Complex Number

JEE Main 2021 · 26 February · Evening Shift · Mathematics · Complex Number

Let z be those complex numbers which satisfy |z + 5| ≤ 4 and z(1 +...

Let zz be those complex numbers which satisfy \left|z + 5\right| \le 4andandz\left(1 + i\right) + \overset{¯}{z}\left(1 - i\right) ⩾ - 10, i = \sqrt{- 1}.Ifthemaximumvalueof. If the maximum value of| z + 1{|}^{2}isis\alpha + \beta\sqrt{2},thenthevalueof(α+β), then the value of \left(\alpha + \beta\right) is

Correct answer

0

Step-by-step solution

Let z=x+iyz = x + iy

Given ∣z+5∣≤4| z + 5 | \le 4

(x+5)2+y2≤16...(1){\left(x + 5\right)}^{2} + {y}^{2} \le 16 . . . \left(1\right)

z(1+i)+z¯(1−i)≥−10z\left(1 + i\right) + \overset{¯}{z}\left(1 - i\right) \ge - 10

\left(z + \overset{¯}{z}\right)+i+ i\left(z - \overset{¯}{z}\right)≥−10\ge - 10

x−y+5≥0...(2)x - y + 5 \ge 0 . . . \left(2\right)

∣z+1∣2=∣z−(−1)∣2| z + 1{|}^{2} = | z - \left(- 1\right){|}^{2}

Let P(−1,0)</p><p>P\left(- 1, 0\right)</p><p>| z + 1{|}_{Max .}^{2} = P{B}^{2}(where(whereBisinis in{3}^{rd}quadrant) </p><p>forpointof</p><p>for point ofintersection </p><p></p><p>\left(x+5)2+y2=16x−y+5=0\begin{array}{ll}{\left(x + 5\right)}^{2} + {y}^{2} = 16 \\ x - y + 5 = 0\end{array}\right\}y = \pm 2\sqrt{2}

A \left(2\sqrt{2} - 5, 2\sqrt{2}\right)B\left(- 2\sqrt{2} - 5, - 2\sqrt{2}\right)

P{B}^{2} = {\left(+ 2\sqrt{2} + 4\right)}^{2} + {\left(2\sqrt{2}\right)}^{2}

∣z+1∣2=8+16+162+8| z + 1{|}^{2} = 8 + 16 + 16\sqrt{2} + 8

α+β2=32+162\alpha + \beta\sqrt{2} = 32 + 16\sqrt{2}

α=32,β=16⇒α+β=48\alpha = 32, \beta = 16 ⇒ \alpha + \beta = 48

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