Let P=\z C: |z+2-3i| 1\ and Q=\z C: z(1+i)+ z(1-i) -8\. Let in P , |z-3+2i| be maximum and minimum at z1 and z2 respectively. If |z1|2+2|z2|2= + 2, where , are integers, then + equals .
Answer
36
Solution
P: disc, centre (-2, 3), radius 1
Q: z=x+iy 2(x-y) -8 x-y+4 0 (half-plane containing C)
∵ distance of C from this line = 1 2<1 ⇒ the line cuts the disc
|z-3+2i| = distance from A(3, -2); line AC (C = centre): x+y=1, perpendicular to x-y+4=0
[figure]
Max: farthest point of the disc on x+y=1: z1= (-2- 1 2, 3+ 1 2 )
Min: foot of perpendicular from A on x-y+4=0: z2= (- 32, 52 )
|z1|2= (2+ 1 2 )2+ (3+ 1 2 )2=14+5 2, 2|z2|2=2 344=17
31+5 2 + =31+5=36
Answer: 36