KEAM 2013 Math Paper

Given straight lines are
x−4y+7=0....(i)
and ‌‌3x−12y+11=0
or ‌‌x−4y+‌

11

3

=0.....(ii)
since, both lines are parallel to each other. So, perpendicular distance between both lines a diameter of circle.∴ Diameter = Distance between parallel tangents
⇒ Diameter =‌

|7− 11 3 |

√1+16

=‌

10

3×√17

Required radius =‌

‌ Diameter ‌

2

=‌

5

3√17