In the Previous Two Problems, Using $u _ { i j }$

In the previous two problems, using $u _ { i j }$ to denote the value of $u$ at the $i , j$ point, the equations for the values of the unknown function at the interior points are Select all that apply.

A) $- 4 u _ { 11 } + u _ { 21 } + u _ { 12 } = 0$
B) $- 4 u _ { 22 } + u _ { 21 } + u _ { 12 } = - 2 / 9$
C) $- 4 u _ { 12 } + u _ { 11 } + u _ { 22 } = - 2 / 9$
D) $- 4 u _ { 21 } + u _ { 11 } + u _ { 22 } = - 2 / 9$
E) $- 4 u _ { 22 } + u _ { 21 } + u _ { 12 } = - 4 / 9$