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