my code is not running

y=(x.*exp(x)+0.3*x-0.5) ./(x-5);

y_prime=((x-5) .*(x.*exp(x)+exp(x)+0.3)-x.*exp(x)+0.3*x-0.5)) ./(x-5) .^2;

x_intial=-1;

epsilon=10^(-6);

newton(@(x)(x.*exp(x)+0.3*x-0.5) ./(x-5),@(x)((x-5).*exp(x)+exp(x)+0.3)-(x.*exp(x)+0.3*x-0.5)) ./(x-5).^2,-1,10(^6))

function [x]= newton(y,y_prime,x_initial,epsilon) 
    x(-1) =x_initial;
    i = 1;
    while abs(y(x(i))>epsilon)
        x(i+1) = x(i) - y(x(i))/y_prime(x(i));
        i = i+1;
    end
    fprintf('this answer is x=%.4f',x(i))
end

[Rik]

Why are you trying x(-1)=x_intitial? Your code looks like x could be a scalar instead.

[edward desmond muyomba]

correct me then please

[Tommy]

In addition to the above comment...

This line:

y_prime=((x-5) .*(x.*exp(x)+exp(x)+0.3)-x.*exp(x)+0.3*x-0.5)) ./(x-5) .^2;

has a syntax error, one too many parentheses. Maybe you mean this instead?

y_prime=((x-5) .*(x.*exp(x)+exp(x)+0.3)-x.*exp(x)+0.3*x-0.5) ./(x-5) .^2;

This line:

newton(@(x)(x.*exp(x)+0.3*x-0.5) ./(x-5),@(x)((x-5).*exp(x)+exp(x)+0.3)-(x.*exp(x)+0.3*x-0.5)) ./(x-5).^2,-1,10(^6))

contains a few syntax errors. You are calling your function, newton, which takes four arguments, but it is a bit hard to tell what each of the four arguments should be. Maybe this is correct?

newton(@(x) (x.*exp(x)+0.3*x-0.5)./(x-5),... first arg
    @(x) ((x-5).*exp(x)+exp(x)+0.3)-(x.*exp(x)+0.3*x-0.5)./(x-5).^2,... second arg
    -1,... third arg
    10^6) % fourth arg

This line:

abs(y(x(i))>epsilon)

MATLAB should be warning you that it is unexpected, because

y(x(i))>epsilon

will return a logical (1 or 0). Do you mean

abs(y(x(i)))>epsilon

instead?

[edward desmond muyomba]

the code is not runing

[Image Analyst]

You need to click the green run triangle. That will run it. What else can I say given the incredibly detailed explanation you gave? ?‍♂️

Attach the entire script -- everything including the part where you define x - with the paper clip icon.

Answer 1

[Deepak Gupta]

Hello Edward,

Looking at your code, seems like you are trying to solve an euqation using Newton's Mathod. I see many errors in your code. So i have written a new code to solve the equation, you are trying to solve. Have added comments along the lines for you to understand.

syms f(x) x; %Symbolic variables needs to be defined before using them
f(x) = (x*exp(x)+0.3*x-0.5)/(x-5); % Equation you want to solve
g = diff(f); %To find the derivative of function
epsilon=1e-6;%Max allowed deviation
x = zeros();
x(1)= -1 ;%In Matlab index starts from 1, so this is the initial value of x. 
%No need to create another variable for it.
i =1;
while(abs(f(x(i)))>epsilon) %Loop should be stopped when tolerance is reached
        y(i) = double(f(x(i))); %If you need function values too, otherwise, not needed
        x(i+1) = x(i) - f(x(i))/g(x(i));% Calculating values for x iteratively
        i = i+1;
end

Thanks,

Deepak

[edward desmond muyomba]

this has worked out thanks pham