1X1+2X2+3X3+4X4+5X5.+98X98+99X99+100X100=?
问题描述:
1X1+2X2+3X3+4X4+5X5.+98X98+99X99+100X100=?
答
=100(100+1)(200+1)/6 =338350
1X1+2X2+3X3+4X4+5X5.+98X98+99X99+100X100=?
=100(100+1)(200+1)/6 =338350