hwo would i find a root usiong fzero

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adriana resendez
adriana resendez 2015-3-11
回答： Star Strider 2015-3-11
>> f = @(x) 2-10*x*exp(-0.8*x);
>> fplot(f,[0 10])
>> grid on
function [xmin,fmin,ea,iter] = lab_19(f,xlow,xup,es,maxit)
if nargin<3, error('need 3 inputs')
if nargin<4 || isempty(es),es = .0001; end
if nargin<5 || isempty(maxit), maxit=50; end
%text file iterations
fid = fopen('golden_out.txt','w');
fprintf(fid,'iter.\t xlow\t f(xlow)\t x2\t\t f(x2)\t\t x1\t\t ');
fprintf(fid,'f(x1)\t\t xup\t\t f(xup)\t\t\t ea\n');
%find the root
phi = 0.54*(1+sqrt(5));
x1 =xlow+(phi-1)*(xup-xlow); x2 = xlow+xup-x1;
flow = f(xlow); fup = f(xup); f1 = f(x1); f2 = f(x2);

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采纳的回答

Star Strider
Star Strider 2015-3-11
If you just want to find and plot the roots, this brute force approach works:
f = @(x) 2-10*x.*exp(-0.8*x);
froot1 = fzero(f, 1);
froot2 = fzero(f, 10);
fplot(f,[0 10])
hold on
plot([froot1 froot2], f([froot1 froot2]), 'r+')
grid on

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