how to find the square root of a number by duplex method and also how to find the square of a number by duplex method

Many of the methods for calculating square roots of a positive real number S require an initial seed value. If the initial value is too far from the actual square root, the calculation will be slowed down. It is therefore useful to have a rough estimate, which may be very inaccurate but easy to calculate. If S ≥ 1, let D be the number of digits to the left of the decimal point. If S < 1, let D be the negative of the number of zeros to the immediate right of the decimal point. Then the rough estimation is this:

If D is odd, D = 2n + 1, then use 

If D is even, D = 2n + 2, then use 

Two and six are used because they approximate the geometric means of the lowest and highest possible values with the given number of digits:  and 

When working in the binary numeral system (as computers do internally), an alternative method is to use  (here D is the number of binary digits).