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Format of return value of user defined function

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Md Monirul Islam
Md Monirul Islam 2017-3-18
编辑： Walter Roberson 2017-3-18
i was using this function below to evaluate a non linear equation with False Position Method. this function is working pretty well but the value it returns is NOT in long format.
for example if i use this function to solve the following non linear equation,
f(x)=10-2.1*x-.01*x^3;
a=4;b=5;
then i get
z=50306586349162394761257938446687780/11523119672512394327137541804059681
how can i resolve this problem?
% this fuction evaluates the root of a equation with
% the use of False Position Method.
tol=1e-5;
FU=f(upper);
FL=f(lower);
while (abs(upper-lower)/upper)>tol
x=lower-((FL*(upper-lower))/(FU-FL));
FX=f(x);
if(FX*FL<0)
upper=x;
elseif(FX*FU<0)
lower=x;
else
break
end
end
end

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采纳的回答

Walter Roberson
Walter Roberson 2017-3-18
With difficulty. Your code does not assign anything to z and your code is not a function so we cannot guess that you assigned an output to z.
But mostly, do not use
syms x
f(x)=10-2.1*x-.01*x^3
Instead use
f = @(x) 10-2.1*x-.01*x^3

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