Consider two quadratic expressions f(x)=ax2+bx+c and g(x)=ax2+px+q (a,b,c,p,q R, b≠p)such that their discriminents are equal. If f(x)=g(x) has a root x=a then.
α will be A.M. of the roots of f(x) = 0 and g(x) = 0
a3+ba+c=a3+pa+q => α= q−cb−p
b2−4ac=p2−4aq
b2−p2 = 4a(c-q)
b+p = 4a(c−q)b−p
b+p =-4aα
α= −(b+p)4a which is A.M of the roots of f(x) and g(x) = 0