If the lines $2 x-3 y=5$ and $3 x-4 y=7$ are two diameters of a circle of radius 7 , then the equation of…

If the lines $2 x-3 y=5$ and $3 x-4 y=7$ are two diameters of a circle of radius 7 , then the equation of the circle is
  1. $x^2+y^2+2 x-4 y-47=0$
  2. $x^2+y^2=49$
  3. $x^2+y^2-2 x+2 y-47=0$
  4. $x^2+y^2=17$

Solution

Since, the lines $2 x-3 y=5$ and $3 x-4 y=7$ are the diameters of a circle. Therefore, the point of intersection is the centre of the circle. On solving the given equations, we get $x=1$ and $y=-1$ ie, the centre of the circle. $\therefore$ Required equation of circle is $ \begin{aligned} & (x-1)^2+(y+1)^2 & =7^2 \\ \Rightarrow & x^2+y^2-2 x+2 y+2 & =49 \\ \Rightarrow & x^2+y^2-2 x+2 y-47 & =0 \end{aligned} $

Asked in: AP EAMCET 2008

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