1*2+2*3+3*4+4*5.11*12+12*13怎么解
来源:学生作业帮助网 编辑:作业帮 时间:2024/08/15 22:36:47
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1*2+2*3+3*4+4*5.11*12+12*13怎么解
1*2+2*3+3*4+4*5.11*12+12*13怎么解
1*2+2*3+3*4+4*5.11*12+12*13怎么解
此类题公式:1*2+2*3+3*4+.+n(n+1)=n(n+1)(n+2)÷3
1*2+2*3+3*4+4*5.11*12+12*13
=12(12+1)(12+2)÷3
=728