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QJEEM23Maaa81: JEE Main 2023 Mathematics - Class 11 JEEM23Maaa81 Solution: Let and . Then is equal to ____________.

Let α=8−14i,A={z∈c:αz−α‾z‾z2−(z‾)2−112i=1}\alpha = 8 - 14i,A = \left\{ {z \in c:{{\alpha z - \overline \alpha \overline z } \over {{z^2} - {{\left( {\overline z } \right)}^2} - 112i}}=1} \right\} and B={z∈c:∣z+3i∣=4}B = \left\{ {z \in c:\left| {z + 3i} \right| = 4} \right\} . Then ∑z∈A∩B(Rez−Imz)\sum\limits_{z \in A \cap B} {({\mathop{\rm Re}\nolimits} z - {\mathop{\rm Im}\nolimits} z)} is equal to ____________.

Step-by-Step Verified Solution

Let z=x+iyz = x + iy

and α=8−14i\alpha = 8 - 14i

αz−α‾ z‾z2−z‾2−112i=1{{\alpha z - \overline \alpha \,\overline z } \over {{z^2} - {{\overline z }^2} - 112i}} = 1

∴\therefore (16y−28x)4xy−112i=1{{(16y - 28x)} \over {4xy - 112i}} = 1

(16y−28x+112)i=4xy(16y - 28x + 112)i = 4xy

∴\therefore z=−7iz = - 7i or 4

Now, z=−7iz = - 7i satisfy B

B:x2+(y+3)2=16B:{x^2} + {(y + 3)^2} = 16

A∩B=(0,−7)A \cap B = (0, - 7)

Rez−lm z=7{\mathop{\rm Re}\nolimits} z - lm\,z = 7

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