Straight Line Question 235
Question: Given a family of lines a $ a(2x+y+4)+b(x-2y-3)=0 $ the number of lines belonging to the family at a distance $ \sqrt{10} $ from $ P(2,-3) $ is
Options:
A) 0
B) 1
C) 2
D) 4
Correct Answer: B $ \Rightarrow 25{{(a+b)}^{2}}=50(a^{2}+b^{2}) $ $ \Rightarrow 25{{(a-b)}^{2}}=0\Rightarrow a=b $ For which we get only line $ 3x-y+1=0 $
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Answer:
Solution:
$ \Rightarrow 5a+5b=\pm \sqrt{10(5a^{2}+5b^{2})} $
BETA
