1.

If the lines `2x+3y+1=0` and `3x-y-4=0` lie along diameters of a circle of circumference `10 pi`, then the equation of the circle isA. `x^(2)+y^(2)+2x-2y-23=0`B. `x^(2)+y^(2)-2x-2y-23=0`C. `x^(2)+y^(2)+2x+2y-23=0`D. `x^(2)+y^(2)-2x+2y-23=0`

Answer» Correct Answer - D
Lines `2x+3y+1=0` and `3x-y-4=0` intersect at (1, -1). So, the coordinates of the centre of the circle are (1,-1) . Let r be the radius of the circle. Then,
Circumference `=10 pi rArr 2pi r = 10 pi rArr r =5`
Hence, the equation of the circle is
` (x-1)^(2)+(y+1)^(2)=5^(2)` or, `x^(2)+y^(2)-2x+2y-23=0`


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