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

  • question_answer
    If \[z=x+iy\] and \[|z-2+i|\,=\,|z-3-i|,\] then locus of z is [RPET 1999]

    A) \[2x+4y-5=0\]

    B) \[2x-4y-5=0\]

    C) \[x+2y=0\]

    D) \[x-2y+5=0\]

    Correct Answer: A

    Solution :

    \[|z-2+i|\,=\,|z-3-i|\]  \[\Rightarrow \] \[|(x-2)+i(y+1)|\] \[=\,|(x-3)\,+i\,(y-1)|\] \[\Rightarrow \] \[\sqrt{{{(x-2)}^{2}}+{{(y+1)}^{2}}}\]=\[\sqrt{{{(x-3)}^{2}}+{{(y-1)}^{2}}}\] \[\Rightarrow \] \[{{x}^{2}}+4-4x+{{y}^{2}}+1+2y={{x}^{2}}+9-6x+{{y}^{2}}+1-2y\] \[\Rightarrow \] \[2x+4y-5=0\].


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