If the circles y^2=a\ a n d\ x^2+y^2-6x-8y+9=0` touch externally then `a=` a. 1 b. `-1` c. `21` d. 16

If the circles x^(2)+y^(2)=9 and x^(2)+y^(2)+8y+C=0 touch each other,then c is equal to

The circles x^(2)+y^(2)-6x-8y=0 and x^(2)+y^(2)-6x+8=0 are

Examine whether the two circles x^2+y^2-2x-4y=0 and x^2+y^2-8y-4=0 touch each other externally or internally .

If the circle x ^(2) + y ^(2) - 6x - 8y+ (25 -a ^(2)) =0 touches the axis of ,y then a equals.

If the circle x ^(2) +y ^(2) - 6x - 8y + (25 -a ^(2)) =0 touches the axis of x, then a equals

If the circle x^(2) + y^(2) = 9 touches the circle x^(2) + y^(2) + 6y + c = 0 internally, then c is equal to

Locus of thews of the centre of the circle which touches x^(2)+y^(2)-6x-6y+14=0 externally and also y-axis is:

If the circle x^(2)+y^(2)+2ax+8y+16=0 touch x-a xi s, then the value of a is +-16 (b) +-4(c)+-8(d)+-1

Two circles x^(2) + y^(2) -2kx = 0 and x^(2) + y^(2) - 4x + 8y + 16 = 0 touch each other externally.Then k is