Methods of computing square roots

There are a numbers of ways to calculate square roots of numbers, and even more ways to estimate them.
The mathematical operation of finding a root is the opposite operation of exponentiation, and therefore involves a similar but reverse thought process.
Firstly, one needs to know how precise the result is expected to be. This is because often square roots are irrational. For example, square root of a nice round whole number 28 is a fraction which in its decimal notation has infinite length, and therefore it is impossible to express it exactly:formula_1
Moreover, for some real numbers the square root is a complex number. For example, square root of -4 is a complex number 2"i" :formula_2
In many cases there may be multiple valid answers. For example, square root of 4 is 2, but -2 is also a valid answer. One can verify that they are both valid answers by squaring each candidate answer and checking if you obtain 4 as the result of verification:formula_3
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Please note that calculating a square root is a special case of the problem of calculating Nth root.
Calculating.
Most calculators provide a function for calculation of a square root.
Estimating.
If the result does not have to be very precise, the following estimation techniques could be helpful: