IIT JEE , AIEEE Forum - Mathematics , Analytical Geometry

naman

The locus of the centre of a circle of radius 2 which rolls on the outside of the circle x²+y²+3x-6y-9=0 is :

A) x²+y²+3x-6y+5

B) x²+y²+3x-6y-31

C) x²+y²+3x-6y+22/4

D) x²+y²+3x-6y+101

sahilmadaan12

the answer is B

sahilmadaan12

the radius of the given circle x2+y2+3x-6y-9=0 is 4.5 units
now if a circle of radius 2 will roll on outside of the above cicle then the distance of the centre of required circle will b at a distance of 6.5 (4.5 + 2)units.......s the locus us option B

krish1092

For finding the centre use (-g,-f).Use (x-h)²+(y-k)²=r² for finding the locus.

PRAM0D

the locus is a circle of radius which is 2 units more than that of the given circle and concentric with it. centre of the given circle is ( -3 / 2 , 3 ) and its radius is 9 / 2.

now, radius of the required circle is 13 / 2 . hence, its equation is (x + 3 / 2)^2 + (y - 3)^2 = 169 / 4

therefore, answer is option b.

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For finding the centre use (-g,-f).Use (x-h)2+(y-k)2=r2 for finding the locus.

For finding the centre use (-g,-f).Use (x-h)²+(y-k)²=r² for finding the locus.