How to find quickly square root of a perfect square polynomial of degree 6?

How to find quickly square root of a perfect square polynomial of degree 6? This is a little method which will enable you to get the answer quickly. Let the polynomail be Px^6+Qx^5+Rx^4+Sx^3+Tx^2+Ux+V. Let its root be ax^3+bx^2+cx+d. a= square root of P. b= Q/2a c= (R-b^2)/2a d= U/2c