Question
If z satisfies ∣ z − 1∣ < ∣ z + 3 ∣, then
= 2z + 3 − i satisfies :
- ∣
− 5 − i ∣ < ∣
+ 3 + i ∣
- ∣
− 5∣ < ∣
+ 3∣ and Re (
) > 1
- Im (i
) < 1
- ∣arg (
− 1) ∣ <
The correct answer is: ∣
− 5∣ < ∣
+ 3∣ and Re (
) > 1
Since ∣ z − 1 ∣ < ∣ z + 3 ∣
\∣ z − 1 ∣2 < ∣ z + 3 ∣2
Þ (z − 1) (
− 1) < (z + 3) (
+ 3)
− z −
+ 1 <
+3z + 9
Þ− 8 < 4z + 4 
Þ−2 < z + 
Þ
Þ
Þ
Þ
ÞRe (ω ) > 1
Again ∣ ω − 5 ∣2 < ∣ ω + 3 ∣2
If 
i.e. if
i.e. if16 < 8ω + 8 
i.e. if 2 < ω +
, which is true.
Thus ∣ ω − 5 ∣ < ∣ ω + 3 ∣ and Re (ω ) > 1
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