问题
解答题
求证:1+2+22+…+25n-1能被31整除.
答案
见解析
1+2+…+25n-1==32n-1=(31+1)n-1
=31n+·31n-1+…+
·31+
-1
=31n+·31n-1+…+
·31
=31·(31n-1+·31n-2+…+
),
∵31n-1,·31n-2,…,
都是整数,
∴原式可被31整除.
求证:1+2+22+…+25n-1能被31整除.
见解析
1+2+…+25n-1==32n-1=(31+1)n-1
=31n+·31n-1+…+
·31+
-1
=31n+·31n-1+…+
·31
=31·(31n-1+·31n-2+…+
),
∵31n-1,·31n-2,…,
都是整数,
∴原式可被31整除.