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A root of a nonzero univariate polynomial P is a value a of x such that P(a) = 0. In other words, a root of P is a solution of the polynomial equation P(x) = 0 or a zero of the polynomial function defined by P. In the case of the zero polynomial, every number is a zero of the corresponding function, and the concept of root is rarely considered.
If x is a simple root of the polynomial , then Laguerre's method converges cubically whenever the initial guess, , is close enough to the root . On the other hand, when x 1 {\displaystyle \ x_{1}\ } is a multiple root convergence is merely linear, with the penalty of calculating values for the polynomial and its first and second derivatives at ...
This polynomial is further reduced to = + + which is shown in blue and yields a zero of −5. The final root of the original polynomial may be found by either using the final zero as an initial guess for Newton's method, or by reducing () and solving the linear equation. As can be seen, the expected roots of −8, −5, −3, 2, 3, and 7 were ...
Starting with the current polynomial P(X) of degree n, the aim is to compute the smallest root of P(x).The polynomial can then be split into a linear factor and the remaining polynomial factor () = ¯ Other root-finding methods strive primarily to improve the root and thus the first factor.
Solutions of the equation are also called roots or zeros of the polynomial on the left side. The theorem states that each rational solution x = p ⁄ q, written in lowest terms so that p and q are relatively prime, satisfies: p is an integer factor of the constant term a 0, and; q is an integer factor of the leading coefficient a n.
It was explained above how R 1 (y), R 2 (y), and R 3 (y) can be used to find the roots of P(x) if this polynomial is depressed. In the general case, one simply has to find the roots of the depressed polynomial P(x − a 3 /4). For each root x 0 of this polynomial, x 0 − a 3 /4 is a root of P(x).
A system of polynomial equations (sometimes simply a polynomial system) is a set of simultaneous equations f 1 = 0, ..., f h = 0 where the f i are polynomials in several variables, say x 1, ..., x n, over some field k. A solution of a polynomial system is a set of values for the x i s which belong to some algebraically closed field extension K ...
P(x) will be divided by Q(x) using Ruffini's rule. The main problem is that Q(x) is not a binomial of the form x − r, but rather x + r. Q(x) must be rewritten as = + = (). Now the algorithm is applied: Write down the coefficients and r. Note that, as P(x) didn't contain a coefficient for x, 0 is written: