- #1
utkarshakash
Gold Member
- 854
- 13
Homework Statement
If |z|=1 and |ω-1|=1, where z, ω [itex]\in[/itex] C, then find the range of [itex] |2z-1|^{2}+|2ω-1|^{2}.[/itex]
Homework Equations
The Attempt at a Solution
Since |ω-1|=1
Squaring both sides and simplifying
[itex] |ω|^{2}=ω+\overline{ω}[/itex]
Also simplifying the expression given in the question
[itex]6-2(z+\overline{z})-2(ω+\overline{ω})+4|ω|^{2}[/itex]
[itex]6-2(z+\overline{z})+2(ω+\overline{ω})[/itex]
Since [itex](ω+\overline{ω})=-1[/itex]
[itex]4-2(z+\overline{z})[/itex]
Since [itex](z+\overline{z}) = 2Re(z)[/itex]
Now the expression reduces to
[itex] \large 4 \left\{ 1-Re(z) \right\} [/itex]
Since |z|=1
∴Locus of z will be a circle with centre at origin and unit radius. So the max Re(z) can be 1 and min Re(z) can be -1. Substituting these in my expression for max and min I get [0,8] but the answer is [2,18].