Circle And System Of Circles Question 52
Question: The length of the tangent from the point (4, 5)to the circle $ x^{2}+y^{2}+2x-6y=6 $ is
[DCE 1999]
Options:
A) $ x=3 $
B) $ y=6 $
C) $ 7x-12y-21=0 $
D) $ 7x+12y+21=0 $
Show Answer
Answer:
Correct Answer: A
Solution:
Let $S_1 = x^2 + y^2 - 2x + 6y + 6 = 0 $ and $S_2 = x^2 + y^2 - 5x + 6y + 15 = 0$,
then common tangent is S1 + S2 = 0
therefore 3x = 9
therefore x = 3.
BETA
