Pair Of Straight Lines Question 97
Question: . The angle between the lines represented by the equation $ ax^{2}+xy+by^{2}=0 $ will be $ 45^{o} $ , if
Options:
A) $ a=1,b=6 $
B) $ a=1,b=-6 $
C) $ a=6,b=1 $
D) None of these
Show Answer
Answer:
Correct Answer: B
Solution:
$ \tan 45{}^\circ =\frac{2\sqrt{\frac{1}{4}-ab}}{a+b} $
$ \Rightarrow {{(a+b)}^{2}}=(1-4ab)\Rightarrow a^{2}+b^{2}+6ab-1=0 $ , which is obviously satisfied by $ a=1 $ and $ b=-6 $ .
BETA
