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A method analogous to piece-wise linear approximation but using only arithmetic instead of algebraic equations, uses the multiplication tables in reverse: the square root of a number between 1 and 100 is between 1 and 10, so if we know 25 is a perfect square (5 × 5), and 36 is a perfect square (6 × 6), then the square root of a number greater than or equal to 25 but less than 36, begins with ...
This happens to coincide with the "Babylonian" method of finding square roots, which consists of replacing an approximate root x n by the arithmetic mean of x n and a ⁄ x n. By performing this iteration, it is possible to evaluate a square root to any desired accuracy by only using the basic arithmetic operations .
The square root of a positive integer is the product of the roots of its prime factors, because the square root of a product is the product of the square roots of the factors. Since p 2 k = p k , {\textstyle {\sqrt {p^{2k}}}=p^{k},} only roots of those primes having an odd power in the factorization are necessary.
A solution in radicals or algebraic solution is an expression of a solution of a polynomial equation that is algebraic, that is, relies only on addition, subtraction, multiplication, division, raising to integer powers, and extraction of n th roots (square roots, cube roots, etc.). A well-known example is the quadratic formula
The square-free factorization of a polynomial p is a factorization = where each is either 1 or a polynomial without multiple roots, and two different do not have any common root. An efficient method to compute this factorization is Yun's algorithm .
In numerical analysis, a root-finding algorithm is an algorithm for finding zeros, also called "roots", of continuous functions. A zero of a function f is a number x such that f ( x ) = 0 . As, generally, the zeros of a function cannot be computed exactly nor expressed in closed form , root-finding algorithms provide approximations to zeros.
A square root of a number x is a number r which, when squared, becomes x: =. Every positive real number has two square roots, one positive and one negative. For example, the two square roots of 25 are 5 and −5. The positive square root is also known as the principal square root, and is denoted with a radical sign:
Babylonian method, for finding square roots of numbers [3] Fixed-point iteration [4] Means of finding zeros of functions: Halley's method; Newton's method; Differential-equation matters: Picard–Lindelöf theorem, on existence of solutions of differential equations; Runge–Kutta methods, for numerical solution of differential equations