题目有误,应该是k²+k²(k+1)²+(k+1)²吧?最后面掉了个²k²+k²(k+1)²+(k+1)²=k²+k²(k²+2k+1)+k²+2k+1=k^4+2k³+3k²+2k+1=(k^4+2k³+k&#...