AP EAMCET Engineering 21 Sep 2020 Shift 2 Paper

(c) It is given that the pair of straight lines
x2−2pxy−y2=0 and x2−2qxy−y2=0 bisect, the angles between each other,
then equations ‌

x2−y2

1−(−1)

=‌

xy

−p

and x2−2qxy−y2=0 represents same line,
so x2+‌

2

p

xy−y2=0 represents x2−2qxy−y2=0 on comparing,
we get ‌

2

p

=−2q ⇒‌‌pq+1=0