5\6-7\12+9\20-11\30+13\42-15\56怎么解

5\6-7\12+9\20-11\30+13\42-15\56怎么解
5\6-7\12+9\20-11\30+13\42-15\56怎么解

5\6-7\12+9\20-11\30+13\42-15\56怎么解
5\6-7\12+9\20-11\30+13\42-15\56
=(1/2+1/3)-(1/3+1/4)+(1/4+1/5)-(1/5+1/6)+(1/6+1/7)-(1/7+1/8)
=1/2+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8
=1/2-1/8
=3/8

= (1/2+1/3) -(1/3+1/4) + (1/4+1/5) - (1/5 + 1/6) + (1/6+1/7) - (1/7+1/8)
= 1/2 - 1/8 = 3/8

=10/12-7/12+9/20-11/30+13/42-15/56
=1/4+9/20-11/30+13/42-15/56
=5/20+9/20-11/30+13/42-15/56
=7/10-11/30+13/42-15/56
=10/30+13/42-15/56
=14/42+13/42-15/56
=27/42-15/56
=9/14-15/56
=36/56-15/56=21/56=3/8