The sum of the square of the modulus of the elements in the set {z=a+ib:a,b∈Z,z∈C,∣z−1∣≤1,∣z−5∣≤∣z−5i∣} is ______.
Answer: 9
Solution
∣z−1∣≤1 over the integer lattice gives (0,0),(1,0),(2,0),(1,1),(1,−1). The condition ∣z−5∣≤∣z−5i∣ reduces to a≥b, which all five satisfy. Sum of ∣z∣2=0+1+4+2+2=9.