原式=（141+1+1/140）x1/141
=(141+141/140)x1/141
=141x1/141+(141/140)x1/141
=1+1/140 原式=（141+1+1/140）x1/141
=(141+141/140)x1/141
=141x1/141+(141/140)x1/141
=1+1/140