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Home  >>  JEEMAIN and NEET  >>  Mathematics  >>  Class11  >>  Coordinate Geometry

If the two circles $(x-1)^2+(y-3)^2=r^2$ and $x^2+y^2-8x+2y+8=0$ intersect in two distinct point then

$\begin{array}{1 1}(A)\;r >2 \\(B)\;2 < r < 8 \\(C)\;r < 2 \\(D)\;r=2 \end{array}$

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1 Answer

$|r_1-r_2| < c_1c_2$ for intersection
=> $r-3 <5 => r <8$ -----(i)
and $r_1+r_2 > c_1c_2$
$r+3 > 5$
=> $r >2$------(ii)
from (i) and (ii) we have $2 < r< 8$
Hence B is the correct answer.
answered Apr 8, 2014 by meena.p
 

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