Circle And System Of Circles Question 263

Question: If the straight line $ y=mx $ is outside the circle $ x^{2}+y^{2}-20y+90=0 $ , then

[Roorkee 1999]

Options:

A) $ m>3 $

B) $ m<3 $

C) $ |m|>3 $

D) $ |m|<3 $

Show Answer

Answer:

Correct Answer: D

Solution:

If the straight line y = mx is outside the given circle then distance from centre of circle > radius of circle $ \frac{10}{\sqrt{1+m^{2}}}>\sqrt{10} $

therefore (1 + m2) < 10

therefore m2 < 9

therefore |m|< 3.