①1+2+3+….…+1999 ②2000-3-6-9-……-51

问题描述:

①1+2+3+….…+1999 ②2000-3-6-9-……-51
①1+2+3+….…+1999 ②2000-3-6-9-……-51-54这两题的步骤

1:
=(1+1999)x1999÷2
=2000x999.5
=19990002:
=2000-[(3+54)x18÷2]
=2000-(57x9)
=2000-513
=1487采纳我吧,求您了,大哥