If the point P(p, q) is equidistant from the points A(a+b, b-a) and B(a-b, a+b), then
- bp + aq = 0
Given that AP = BP
∴AP2=BP2⇒(a+b−p)2+(b−a−q)2=(a−b−p)2+(a+b−q)2⇒a2+b2+p2+2ab−2bp−2ap+b2+a2+q2−2ab+2aq−2bq=a2+b2+p2−2ab+2bp−2ap+a2+b2+q2+2ab−2bq−2aq
⇒2ab−2bp−2ap−2ab+2aq−2bq=−2ab+2bp−2ap+2ab−2bq−2aq
⇒−4bp+4qa=0⇒−bp+aq=0