Getting Error: Unexpected MATLAB expression.

Question: Use Newton's method to nd three roots of x^3 - 5x + 1 = 0 accurate to within 10^-14.

My Matlab Code:

format long
x=0.5
for I = 1:10
x=x-((x.^3)-5.x+1)/(3.(x.^2)-5),
end
x=x-((x.^3)-5.x+1)/(3.(x.^2)-5),
             |
Error: Unexpected MATLAB expression.

Problem: I am getting the aforementioned error and therefore, cannot find roots of the given equation in the question. Please can you find the problem and help me out? I am new to Matlab and I am learning this software. Thanks a lot! Appreciate it. :)

MATLAB Version: MATLAB R2013a

Answer 1

[Star Strider]

Change it to:

x=x-((x.^3)-5.*x+1)./(3.*(x.^2)-5);

It’s missing two multiplication asterisks and a dot before the division sign.

[Image Analyst]

The dot before the / is actually not needed since the denominator is a scalar, not an array, though it does not hurt to have it.

[Star Strider]

I agree. In all functions and most of my Answers, I vectorise everything, unless I know the intent are matrix operations.

[John]

Thanks Star Strider and Image Analyst! It worked. :)

[Star Strider]

My (our) pleasure!

Answer 2

[M SEETHA]

IE11=(P*Ie)*((alpha*P^(-neta))*(M^2/2)+(beta*P^(-neta))*(Pr+(xi-1)*alpha*P^(-neta)/B)*(M^2/2)-(t^2/2B^2)*(B^2*e^(-B*tp)+(1-e^(-B*M))));

THIS SHOWS UNEXPECTED MATLAB EXPRESSION KINDLY HELP ME

[Walter Roberson]

(t^2/2B^2) is missing an operation between the 2 and the B

I would suggest to you that the e^ parts are confusing. People are going to wonder why you named a variable e that is not the base of natural logarithms and raise it to a power. We know that it is not the base of the natural logarithms because if it were you would have coded exp() instead. Use a different variable name for whatever your e is, such as "emissivity" so readers do not get confused thinking it is an exp() operation when it is not.