subscript indices error with function file (bisection method)

function result=guess(x)
xleft=x(1,1);
xright=x(1,2);
f(x)= x.^3 - 4.9*x.^2 +6.76*x-2.013
if f(xleft)*f(xright)<0
    result= 'guess is valid'
else 
    result= 'guess is not valid'
end

I enter in x=[0,1] and I want my program to define xleft as 0 and xright as 1 and then multiply f(0) with f(1) and tell me whether the product is <0 or not. Why won't it do this?

Also, if I wanted to enter in a matrix like x=[0,1;1,3;5,0] Then I would do

f= x.^3 - 4.9*x.^2 +6.76*x-2.013
for ii=1:3
    xleft=x(ii,1)
    xright=x(ii,2)

But this won't work either.

Answer 1

[Walter Roberson]

f(x)= x.^3 - 4.9*x.^2 +6.76*x-2.013

looks like you are trying to define a formula, not trying to calculate a value based upon specific x. You should probably be using

f = @(x) x.^3 - 4.9*x.^2 +6.76*x-2.013;

Answer 2

[Nilesh Bhosale]

Give simple program of Bisection method

[Walter Roberson]

That does not appear to be an Answer to this Question?