MATLAB: How to fit a polynom to known points without polyfit

fit polynomMATLABplotpolypolyfitpolynompolyval

Hello there,
I'm new to matlab and I was given the task to fit a polynom to a set of known points without using polyfit by my teacher. I've been dabbling around for hours now and I just can not figure it out.
Here are the given Points:
(-3|0) (-2|0) (-1|0) (0|0) (2|0) (2.5|0)
And I was given the Point (1|1)
I figured out how to fit the polynom to the y=0 points but I can not figure out how to fit it to the (1|1)
Here is my code so far (without the plot)
x = linspace(-4,3,701)' ; % x-Achse
NSx = [ -3 -2 -1 0 2 2.5 ]'; % Bekannte Werte x
% 

% y1 = 0;
% 
ko = 0;
p = poly(NSx);
y1 = polyval(p,x);
Can somebody please help me solve this issue?
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