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AP EAMCET · Maths · Complex Number

The locus of the point representing the complex number \(z\) for which \(|z+3|^2-|z-3|^2=15\) is

  1. A a circle
  2. B a parabola
  3. C a straight line
  4. D an ellipse
Verified Solution

Answer & Solution

Correct Answer

(C) a straight line

Step-by-step Solution

Detailed explanation

Let the comlex number, \(z=x+i y\) Now, \(|z+3|^2-|z-3|^2=15\) \(\begin{aligned} & \therefore \quad|x+i y+3|^2-|x+i y-3|^2=15 \\ & (x+3)^2+y^2-(x-3)^2-y^2=15 \\ & x^2+6 x+9-x^2+6 x-9=15 \\ & 12 x=15 \Rightarrow 4 x=5 \end{aligned}\) \(\therefore\) It represents a straight line.