Answers

2014-05-21T12:18:12+08:00
Let (a,b) be the center.

the radius is sqrt( [a+2]^2 + [b-3]^2 )
same with. its distance from (a,b) to the line x = 6. which is |a-6|

comparing the 2 radii,

[a+2]^2 + [b-3]^2 = (a-6)^2

a^2 + 4a + 4 + b^2 - 6b + 9 = a^2 - 12a + 36

16a + b^2 - 23 - 6b = 0

a = x, b = y.

16x + y^2 - 23 - 6y = 0.

therefore, the locus is y^2 - 6y - 23 + 16x = 0.
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