Let P=z∈ mathbbC:|z+2-3i|≤ 1 and Q=z∈ mathbbC:z(1+i)+ z(1-i)≤ -8. Let in P∩ Q,|z-3+2i| be maximum and minimum at z_1 and z_2 respectively. If…
JEE Main 2024 — Mathematics Algebra
2024integerhard
Let P=z∈C:∣z+2−3i∣≤1 and Q=z∈C:z(1+i)+zˉ(1−i)≤−8. Let in P∩Q,∣z−3+2i∣ be maximum and minimum at z1 and z2 respectively. If ∣z1∣2+2∣z∣2=α+β2, where α,β are integers, then α+β equals __________
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Held on 1 Feb 2024 · Verified 6 Jul 2026.
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Solution
Given: ∣z+2−3i∣≤1
Putting, z=x+iy.
⇒(x+2)2+(y−3)2≤1...(i)
For the circle represented in equation (i), centre is (−2,3) and radius, r=1.
It is given that, z(1+i)+z(1−i)≤−8
⇒(x+iy)(1+i)+(x−iy)(1−i)≤−8
⇒x+ix−y+iy+x−ix−iy−y≤−8
⇒2x−2y≤−8
⇒x−y+4=0
So, the line passing through (3,−2) and perpendicular to x−y+4=0 is given by, x+y−1=0.
So, the distance of line x−y+4=0 from the centre (−2,3) is given by,
d=∣2−2−3+4∣
⇒d=21
Now, x+y−1=0 can be rewritten as,
2−1x+2=21y−3=CAorCB
For CA=2−1 and CB=1, A≡(2−3,25) and B≡(2−1−2,21+3).
⇒∣z1∣2=(2+21)2+(3+21)2
⇒∣z1∣2=4+21+22+9+21+32
⇒∣z1∣2=14+52
⇒∣z2∣2=2(49+425)
⇒∣z2∣2=17
⇒∣z1∣2+2∣z2∣2=31+52
⇒α=31,β=5
⇒α+β=36
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