Circle And System Of Circles Question 105
Question: The equation of the circle which touches x-axis and whose centre is (1, 2), is
[MP PET 1984]
Options:
A) $ x^{2}+y^{2}-2x+4y+1=0 $
B) $ x^{2}+y^{2}-2x-4y+1=0 $
C) $ x^{2}+y^{2}+2x+4y+1=0 $
D) $ x^{2}+y^{2}+4x+2y+4=0 $
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Answer:
Correct Answer: B
Solution:
Centre (1, 2) and since circle touches x-axis, therefore, radius is equal to 2.
Hence the equation is $ {{(x-1)}^{2}}+{{(y-2)}^{2}}=2^{2} $
$ \Rightarrow x^{2}+y^{2}-2x-4y+1=0 $ . Trick : The only circle is $ x^{2}+y^{2}-2x-4y+1=0 $ , whose centre is (1, 2).
BETA
