Let the complex numbers and 1 lie on the circles |z-z0 |2=4 and |z-z0 |2=16 respectively, where z0=1+i. Then, the value of 100| |2 is .
Answer
20
Solution
Let r=| |2; |z0|2=2. Use |a-b|2=|a|2+|b|2-2 Re(a b)
| -z0|2=4 r+2-2 Re( z0)=4 2 Re( z0)=r-2
1 = r: | r-z0 |2=16 1r+2- 2 Re( z0)r=16
1-(r-2)r=14 3-r=14r r= 15
100| |2=20
Answer: 20