If z is a complex number such that ∣z∣≥1, then the minimum value of z+21(3+4i) is:
(A)25
(B)2
(C)3
(D)23
Solution
The expression z+23+2i represents the distance from z to the point −23−2i. The distance from the origin to this point is −23−2i=49+4=25. Since ∣z∣≥1, the set of possible z is the exterior (including boundary) of the unit circle. The minimum distance from this set to −23−2i is 25−1=23. However, the source solution notes that the minimum value is actually zero, which would occur if z=−23−2i, but ∣z∣=25>1, so this is valid. The source answer is marked as Bonus, indicating an issue with the problem statement or options.
JEE Main · 2024 · 01 Feb 2024 · Shift 2 · Single correct option