20*20-19*19+18*18-17*17+16*16-15*15+……+2*2-1*1用简便方法!
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/15 19:30:20
![20*20-19*19+18*18-17*17+16*16-15*15+……+2*2-1*1用简便方法!](/uploads/image/z/15120960-24-0.jpg?t=20%2A20-19%2A19%2B18%2A18-17%2A17%2B16%2A16-15%2A15%2B%E2%80%A6%E2%80%A6%2B2%2A2-1%2A1%E7%94%A8%E7%AE%80%E4%BE%BF%E6%96%B9%E6%B3%95%21)
20*20-19*19+18*18-17*17+16*16-15*15+……+2*2-1*1用简便方法!
20*20-19*19+18*18-17*17+16*16-15*15+……+2*2-1*1用简便方法!
20*20-19*19+18*18-17*17+16*16-15*15+……+2*2-1*1用简便方法!
20*20-19*19+18*18-17*17+16*16-15*15+……+2*2-1*1
=(20+19)(20-19)+(18+17)(18-17)+……(2+1)(2-1)
=(20+19)+(18+17))+……(2+1)
=20+19+18+17+……+2+1
=(20+1)*20/2
=210