If the two pairs of line `x^2 -2mxy -y^2=0 and x^2 - 2nxy -y^2 = 0` are such that one of them represent the bisector of the angles between the other, then: (A) mn + 1 = 0 (B) mn - 1 = 0 (C) 1/m + 1/n = 0 (D) 1/m -1/n = 0

If the pairs of lines x^(2) – 2nxy - y^(2) = 0 and x^(2) – 2mxy - y^(2) = 0 are such that one of them represents the bisectors of the angles between the other, then

If the pairs of lines x^(2) - 2nxy -y^(2) =0 and x^(2) - 2mxy -y^(2) =0 are such that one of them represents the bisector of the angles between the other , then a): (1)/(n) +(1)/(m) =0 b) (1)/(n) - (1)/(m) =0 c) nm-1 =0 d) nm+1=0

If the pair of lines represented by x^2 - 2pxy - y^2= 0 and x^2 - 2qxy - y^2 = 0 be such that each pair bisects the angle between the other pair, then prove that pq = -1 .

If the of lines represented by x^2-2cxy-y^2= 0 and x^2-2dxy-y^2=0 be such that each pair bisects the angle between the other pair, prove that cd = -1.

The equation of the bisector of the obtuse angle between the lines x-y+2=0 , 7x+y+1=0 is

The equation of the bisector of the obtuse angle between the lines x -y+2=0, 7x+y+1=0 is