If a root of the equation ax2+bx+c=0 be reciprocal of the equation then a′x2+b′x+c′=0, then
(cc′−aa′)2=(ba′−cb′)(ab′−bc′).
Let α be a root of first equation, then 1α be a root of second equation.
therefore aα2+bα+c=0 and a′1α2+b′1α+c′=0 or c′α2+b′α+d=0
Hence α2ba′−b′c=αcc′−aa′=1ab′−bc′
(cc′−aa′)2=(ba′−cb′)(ab′−bc′).