Q.

If one of the diameters of the circle x2+y2–10x+4y+13=0 is a chord of another circle C, whose centre is the point of intersection of the lines 2x + 3y = 12 and 3x –2y = 5, then the radius of the circle C is :          [2024]

1 6  
2 4  
3 20  
4 32  

Ans.

(1)

Given, 2x + 3y = 12

3x – 2y = 5

Point of intersection = (3, 2)

∴  Centre is (3, 2)

      l=4+16=25

      l2+R2=r2

⇒ 20+(25+4–13)=r2

⇒ 20+16=r2 ⇒ r=6