How to plot a polynomial?

Hi I am trying to plot this polynomial but it keeps graphing as a straight line. Can anyone help?

%% Part 2

% This is the graphing portion of the problem

xi = [0,7];

fend = -2+(6.*xi)-(4.*(xi.^2))+(.5.*(xi.^3));

plot(xi,fend,'r');

xlabel('X');

ylabel('f(x)');

title('Root Find of F(x) = -2+6x-4x^2+0.5x^3');

Answer 1

[Sam Chak]

Hi @Sarah Elena Aiko Johnson

Should try like this:

xi = linspace(-2, 8, 101);
fend = - 2 + (6*xi) - 4*(xi.^2) + (0.5*(xi.^3));
plot(xi,fend,'r');
xlabel('X');
ylabel('f(x)');
title('Root Find of F(x) = -2+6x-4x^2+0.5x^3');

[Sam Chak]

xi = [0,7]

xi = 1×2

0 7

fend = -2+(6.*xi)-(4.*(xi.^2))+(.5.*(xi.^3))

fend = 1×2

-2.0000 15.5000

@Sarah Elena Aiko Johnson, the reason is because there only two points in . When they are passed to fend for evaluation, it will also return two points.

And when you attempt to plot (connect a line between two points), it definitely gives a straight line. In my Answer, I created 101 data points between .