Mathematics · Complex Numbers

JEE Main 2024 — 1 February, Shift 1 — Question 27

Let P={z∈C:∣z+2−3i∣≤1}\mathrm{P}=\{\mathrm{z} \in \mathbb{C}:|\mathrm{z}+2-3 \mathrm{i}| \leq 1\} and Q={z∈C:z(1+i)+z‾(1−i)≤−8}\mathrm{Q}=\{\mathrm{z} \in \mathbb{C}: \mathrm{z}(1+\mathrm{i})+\overline{\mathrm{z}}(1-\mathrm{i}) \leq-8\}. Let in P∩Q,∣z−3+2i∣\mathrm{P} \cap \mathrm{Q},|\mathrm{z}-3+2 \mathrm{i}| be maximum and minimum at z1z_{1} and z2z_{2} respectively. If ∣z1∣2+2∣z∣2=α+β2\left|z_{1}\right|^{2}+2|z|^{2}=\alpha+\beta \sqrt{2}, where α,β\alpha, \beta are integers, then α+β\alpha+\beta equals \qquad ・

Answer: 36

Numerical answer — enter this value.

Step-by-step solution

Clearly for the shaded region z1\mathrm{z}_{1} is the intersection of the circle and the line passing through P(L1)\mathrm{P}\left(\mathrm{L}_{1}\right) and z2z_{2} is intersection of line L1&L2L_{1} \& L_{2}

Circle : (x+2)2+(y−3)2=1(x+2)^{2}+(y-3)^{2}=1

L1:x+y−1=0\mathrm{L}_{1}: \mathrm{x}+\mathrm{y}-1=0

L2:x−y+4=0\mathrm{L}_{2}: \mathrm{x}-\mathrm{y}+4=0

On solving circle &L1\& L_{1}

we get z1:(−2−12,3+12)z_{1}:\left(-2-\frac{1}{\sqrt{2}}, 3+\frac{1}{\sqrt{2}}\right)

On solving L1L_{1} and z2z_{2} is intersection of line L1&L2L_{1} \& L_{2}

we get z2:(−32,52)z_{2}:\left(\frac{-3}{2}, \frac{5}{2}\right)

∣z1∣2+2∣z2∣2=14+52+17=31+52\begin{aligned} & \left|z_{1}\right|^{2}+2\left|z_{2}\right|^{2}=14+5 \sqrt{2}+17 & =31+5 \sqrt{2} \end{aligned}

So α=31\alpha=31

β=5\beta=5

α+β=36\alpha+\beta=36

Solution figure

Answer key and solution verified before publishing.

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Exam
JEE Main 2024
Subject
Mathematics
Chapter
Complex Numbers
Topic
Geometry of Complex Numbers