svetazuna 3m - (4n²-8n+4) / (2n²+2n+2) : (n-2) / (n³+n²+n) = 
3m - 4*(n²-2n+1) / 2*(n²+n+1) : (n-2) / (n²+n+1)*n = 
3m - 4*(n²-2n+1) / 2*(n²+n+1) *(n²+n+1)*n /  (n-2) = 
3m - 2n*(n²-2n+1) / (n-2).

при n = -2,m = -1 /3:
3*(-1/3) - 2*(-2)*(4+4+1) /(-2-2) = 
-1 + 4*9/(-4) = -1 - 9 = -10