1x2+2x3+3x4+...+n(n+1)=?1x2x3+2x3x4+3x4x5+...+n(n+1)(n+2)=?
问题描述:
1x2+2x3+3x4+...+n(n+1)=?1x2x3+2x3x4+3x4x5+...+n(n+1)(n+2)=?
答
1x2+2x3+3x4+...+n(n+1)=?1x2x3+2x3x4+3x4x5+...+n(n+1)(n+2)=?