Two curves `ax^2+2hxy+by^2-2gx-2fy+c=0 and a'x^2-2hxy+(a'+a-b)y^2-2g;x-2f'y+c=0` intersect in four concyclic points `A.B.C and D.` If be the point `((g+g')/(a+a'),(f+f')/(a+a'))` then `(PA^2)/(PD^2)+(PB^2)/(PD)^2+(PC)^2/(PD)^2` is equal to