Решение диф. уравнения 2 порядка методом Рунге-Кутты 4 порядка точности

u'[x] = v[x], f[x, u, v] == v'[x], g[x] == u'[x]
f[x_, u_, v_] := 2*u[x] + v[x] - 1 - 2*x
g[x_] := v[x]
Subscript[x, 0] = 0, Subscript[u, 0] = 3, Subscript[v, 0] = -2;
Subscript[x, n] = 1, n = 20, h = (Subscript[x, n] - Subscript[x, 0])/n;
q = {"i", "\!\(\*SubscriptBox[\(x\), \(i\)]\)", 
   "\!\(\*SubscriptBox[\(u\), \(i\)]\)"};
x = Subscript[x, 0], u = Subscript[u, 0], v = Subscript[v, 0];
Do[k1 = Subscript[v, i], 
 l1 = f[Subscript[x, i], Subscript[u, i], Subscript[v, i]];
 k2 = Subscript[v, i] + (h/2)*l1, 
 l2 = f[Subscript[x, i] + h/2, Subscript[u, i] + (h/2)*k1, 
   Subscript[v, i] + (h/2)*l1];
 k3 = Subscript[v, i] + (h/2)*l2, 
 l3 = f[Subscript[x, i] + h/2, Subscript[u, i] + (h/2)*k2, 
   Subscript[v, i] + (h/2)*l2];
 k4 = Subscript[v, i] + h*l3, 
 l4 = f[Subscript[x, i] + h, Subscript[u, i] + h*k3, 
   Subscript[v, i] + h*l3];
 k = (k1 + 2*k2 + 2*k3 + k4)/6;
 l = (l1 + 2*l2 + 2*l3 + l4)/6;
 Subscript[u, i + 1] = Subscript[u, i] + h*k;
 Subscript[v, i + 1] = Subscript[v, i] + h*l;
 e[i] = {i, Subscript[x, i], Subscript[u, i]};
 Subscript[x, i + 1] = Subscript[x, i] + h, {i, 0, n}]
q2 = Table[e[i], {i, 0, n}];
N[Join[{q}, q2], 6] // TableForm