令x=1x2+2x3+3x4+4x5+5x6+······+99x100
=[1x1+1]+[2x2+2]+[3x3+3]+[4x4+4]+.+[99x99+99]
=1x1+2x2+3x3+4x4+.+99x99+(1+2+3+4+.+99)
=99x(99+1)x(99+2)/6+99x(99+1)/2
=99x50x37+99x50
=99x50x38
=188100跟答案错了。。答案是有的，但是不知道什么意思不好意思，我写错呢x=1x2+2x3+3x4+4x5+5x6+······+99x100=[1x1+1]+[2x2+2]+[3x3+3]+[4x4+4]+.....+[99x99+99]=1x1+2x2+3x3+4x4+....+99x99+(1+2+3+4+....+99)=99x(99+1)x(99x2+1)/6+99x(99+1)/2=33x50x199+99x50=333300