Secante

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%             -------------                             ---------
%             function file                             secante.m
%             -------------                             ---------

	function [x] = secante(x1,x2,epsilon)
    %==========================================================
     format long
     x=[];
     max=50;
	 x(1)=x1;
     x(2)=x2;
     fx1 = x(1)^5 + (-10/9)*(x(1))^3 +(5/21)*x(1);
     
     for k=3:max
         
         fx2 = (x(k-1))^5 + (-10/9)*(x(k-1))^3 +(5/21)*x(k-1);
         
         derivada=(fx2 - fx1)/(x(k-1) - x(k-2));
         
         % Nova Aproximacao
	     x(k)  =  x(k-2) - (fx1/derivada);  
         
         fxk = (x(k))^5 + (-10/9)*(x(k))^3 +(5/21)*x(k);
         
         errox=abs(x(k)-x(k-1));
         
         errof=abs(fxk);
         
         if (errox < epsilon) & (errof < epsilon)
             break
         end    
         fx1=fx2;
     end
     %==========================================================