Three Point Formula

A three point formula can be constructed which uses the difference in results of the forward and backward two point difference schemes, and computes a three point derivative of that to get the second derivative.
 

Three Point Formula

Input Data

$$x_0=0,\ x_1=1,\ x_2=2$$ $$y_0=1,\ y_1=4,\ y_2=9$$

Solution

$$Ans=2$$

A three point formula can be constructed which uses the difference in results of the forward and backward two point difference schemes, and computes a three point derivative of that to get the second derivative.