∵上述各等式可整理为:3 2-1 2=2×4;
4 2-2 2=3×4;
5 2-3 2=4×4;
6 2-4 2=5×4;
从而可得到规律为:(n+2) 2-n 2=4(n+1).
故答案为:(n+2) 2-n 2=4(n+1).