Theorem 1.5(Newton-Raphson Theorem). Assume that f E Ca, b and there exists a number p e la, 6, where f(p)=0. If f(p)#0, then there exists a 8>0 such hat the sequence pklk-o defined by the iteration P=9(h-1)=pk-1 f(pk-1) for k= 1.2 will converge to p for any initial approximation Po E lp-8, p+8 Remark. The function g()defined by formula 9()=x