Subscript[U, 0][Subscript[x, 1]] =
U[Subscript[x, 1]] + h*Subscript[f, 1][Subscript[x, 1]] +
h^2*Subscript[f, 2][Subscript[x, 1]]
Subscript[V, 0][Subscript[x, 1]] =
V[Subscript[x, 1]] + h*Subscript[g, 1][Subscript[x, 1]] +
h^2*Subscript[g, 2][Subscript[x, 1]]
Subscript[U, 2][Subscript[x,
1]] = -((A1111 (Subscript[U, 0]^\[Prime]\[Prime])[Subscript[x, 1]])/
A2121) + (
A1122 (A1122 + A1221) (Subscript[U, 0]^\[Prime]\[Prime])[Subscript[
x, 1]])/(A2121 A2222)
Subscript[V, 2][Subscript[x,
1]] = -((A1212 (Subscript[V, 0]^\[Prime]\[Prime])[Subscript[x, 1]])/
A2222) + ((A1122 + A1221) (Subscript[V, 0]^\[Prime]\[Prime])[
Subscript[x, 1]])/A2222
想让输出的U2[X1]用U0和V0及其导数表示，求助各位大佬。

权宜之计：Subscript[U, 0][x_]=U[Subscript[x, 1]]+h Subscript[f, 1][Subscript[x, 1]]+h^2 Subscript[f, 2][Subscript[x, 1]]/.Subscript[x, 1]->x
新手最好不要用下标。