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} and Q={z∈C:z(1+i)+z¯(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 __________
Correct answer
0
Step-by-step solution
Given: ∣z+2−3i∣≤1
Putting, z=x+iy.
⇒(x+2)2+(y−3)2≤1...(i)
For the circle represented in equation \left(i\right),centreis(−2,3)andradius,r = 1.</p><p>Itisgiventhat,z\left(1 + i\right) + z \left(1 - i\right) \le - 8</p><p>⇒ \left(x + iy\right)\left(1 + i\right) + \left(x - iy\right)\left(1 - i\right) \le - 8</p><p>⇒ x + ix - y + iy + x - ix - iy - y \le - 8</p><p>⇒ 2x - 2y \le - 8</p><p>⇒ x - y + 4 = 0</p><p>So,thelinepassingthrough(3,−2)andperpendiculartox - y + 4 = 0isgivenby,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,thedistanceoflinex - y + 4 = 0fromthecentre(−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).