f = @(x) sqrt(x+1);
fTriplePrime = MAKE FUNC DECLERATION HERE;

for i = 1:4
  h = 2^(-2*(i+1));
  forward = (f(x + h) - f(x))/h;
  doubleCenter = (f(x + h) - f(x - h))/h - (1/6)*h^2*fTriplePrime(a,b);
end