The number of elements in the set { z = a + i b ∈ ℂ : a , b ∈ ℤ and 1 < z - 3 +…

The number of elements in the set {z=a+ib:a,b and 1<z-3+2i<4} is _____.

Solution

We know that z-3-2i=r represents a circle with centre 3,-2 and radius r.

1<z-3+2i<4

1<a-32+b+22<16

The ordered pairs of a,b satisfying the above inequality are 0,±2,±2,0,±1,±2,±2,±1

±2,±3,3±,±2,±1,±1,2±,±2

±3,0,0,±3,±3±1,±1,±3

i.e. total 40 elements are present in the given set

Asked in: JEE Main 2022 (28 Jun Shift 1)

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