139x137/138+137x1/138
来源:学生作业帮 编辑:搜搜考试网作业帮 分类:数学作业 时间:2024/06/24 01:54:20
139x137/138+137x1/138
奥数减算:1993x1994-1/1993+1992x1994
奥数减算:1993x1994-1/1993+1992x1994
![139x137/138+137x1/138](/uploads/image/z/17367870-30-0.jpg?t=139x137%2F138%2B137x1%2F138)
139x137/138+137x1/138
=(138+1)x(138-1)/138+137x1/138
=(138^2-1)/138+137x1/138
=138^2/138+(137-1)/138
=138+136/138
=138+68/69
=138又69分之68
1993x1994-1/1993+1992x1994
分子=1993x(1993+1)-1
=1993^2+1993-1
=1993^2+1992
分母=1993+(1993-1)x(1993+1)
=1993+1993^2-1
=1993^2+1992
所以1993x1994-1/1993+1992x1994=1
=(138+1)x(138-1)/138+137x1/138
=(138^2-1)/138+137x1/138
=138^2/138+(137-1)/138
=138+136/138
=138+68/69
=138又69分之68
1993x1994-1/1993+1992x1994
分子=1993x(1993+1)-1
=1993^2+1993-1
=1993^2+1992
分母=1993+(1993-1)x(1993+1)
=1993+1993^2-1
=1993^2+1992
所以1993x1994-1/1993+1992x1994=1