Q32 / 90 · JEE Main 2024 (01 Feb Shift 1) · Mathematics

Let P=z∈ℂ:z+2−3i≤1 and Q=z∈ℂ:z1+i+z¯1−i≤−8. Let in P∩Q,z−3+2i be maximum and minimum at z1 and z2 respectively. If z12+2z2=α+β2, where α,β are integers, then α+β equals __________

Correct answer: 36

Solution

Given: z+2-3i≤1

Putting, z=x+iy.

⇒x+22+y-32≤1   ...i

For the circle represented in equation i, centre is -2,3 and radius, r=1.

It is given that, z1+i+z1-i≤-8

⇒x+iy1+i+x-iy1-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.

Figure

So, the distance of line x-y+4=0 from the centre -2,3 is given by,

d=-2-3+42

⇒d=12

Now, x+y-1=0 can be rewritten as,

x+2-12=y-312= CA or CB

For CA=-12 and CB=1, A≡-32,52 and B≡-12-2, 12+3.

⇒z12=2+122+3+122

⇒z12=4+12+22+9+12+32

⇒z12=14+52

⇒z22=294+254

⇒z22=17

⇒z12+2z22=31+52

⇒α=31, β=5

⇒α+β=36

Hence, the correct answer is 36.

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