If the lines (p−q)x2+2(p+q)xy+(q−p)y2=0 are mutually perpendicular, then
p and q may have any value
Pair of straight lines represented by a second degree equation with coefficient of x2 as a and coefficient of y2 as b are perpendicular if a+b = 0. Herere a + b = 0 for every p and q.