GATE 2020 Civil Engineering Q27

Question

A continuous function f(x) is defined. If the third derivative at $x_i$ is to be computed by using the fourth order central finite-divided-difference scheme (with step length = h), the correct formula is

Accepted Answer

D

Answer

$f'''(x_i) = \frac{-f(x_{i+3})+8f(x_{i+2})-13f(x_{i+1})+13f(x_{i-1})-8f(x_{i-2})+f(x_{i-3})}{8h^3}$

Answer

$f'''(x_i) = \frac{f(x_{i+3})-8f(x_{i+2})-13f(x_{i+1})+13f(x_{i-1})+8f(x_{i-2})+f(x_{i-3})}{8h^3}$