Taylor series f(xᵢ₊₁)=f(xᵢ)+f'(xᵢ)h+(f''(xᵢ)/2!)h²+(f'''(xᵢ)/3!)h³+.....
given f''(xᵢ)=(-f(xᵢ₊₃)+4f(xᵢ₊₂)-5f(xᵢ₊₁​)+2f(xᵢ))/h²

derive the second derivative of forward finite difference n=3
what is the order of error ?