Question

The radius of the circle$\left| \frac{z - i}{z + i} \right|$= 5 is given by –

• A. $\frac{13}{12}$
• B. $\frac{5}{12}$
• C. 5
• D. 625

Answer 1

Answer: (B)

$\frac{5}{12}$

Answer 2

Sol. | z – i | = 5 | z + i |

Ž x² + (y – 1)² = 25{(x² + (y + 1)²}

Eq. of circle is 24x² + 24y² + 52y + 24 = 0

r = $\sqrt{g^{2} + f^{2} - c}$= $\frac{5}{12}$