JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Geometry of complex numbers

  • question_answer
    The equation \[|z-5i|\div |z+5i|\,=12,\] where \[z=x+iy,\] represents a/an [AMU 1999]

    A) Circle

    B) Ellipse

    C) Parabola

    D) No real curve

    Correct Answer: A

    Solution :

    \[\frac{|z-5i|}{|z+5i|}=12\]Þ \[\frac{{{x}^{2}}+{{(y-5)}^{2}}}{{{x}^{2}}+{{(y+5)}^{2}}}=12\] \[\Rightarrow \,\,\,{{x}^{2}}+{{y}^{2}}+25-10y\]\[=12\,[{{x}^{2}}+{{y}^{2}}+25+10y]\] \[\Rightarrow \,\,11{{x}^{2}}+11{{y}^{2}}+130y+275=0.\] Which represents the equation of a circle.


You need to login to perform this action.
You will be redirected in 3 sec spinner