function y=funprime(poly,X,Y,x)

if poly ==1
    y=LagrangeDeriv(X,Y,x);
elseif poly == 2 
    y=DivdiffDeriv(X,Y,x);
elseif poly == 3
    y=NevilleDeriv(X,Y,x);
else 
    y=9*(x-1)^8;
end