Pair Of Straight Lines Question 127

Question: If one of the lines of the pair $ ax^{2}+2hxy+by^{2}=0 $ bisects the angle between positive directions of the axes, then a, b, h satisfy the relation

[Roorkee 1992]

Options:

A) $ a+b=2|h| $

B) $ a+b=-2h $

C) $ a-b=2|h| $

D) $ {{(a-b)}^{2}}=4h^{2} $

Show Answer

Answer:

Correct Answer: B

Solution:

Bisector of the angle between positive directions of the axes is $ y=x $ .

Since it is one of the lines of the given pair $ ax^{2}+2hxy+by^{2}=0, $ we have $ x^{2}(a+2h+b)=0 $ or $ a+b=-2h $ .