一楼很快嘛,但第二题算错了哦
① 4/3-7/12+9/20-11/30+13/42-15/56
=(1+1/3)-(1/3+1/4)+(1/4+1/5)-(1/5+1/6)+(1/6+1/7)-(1/7+1/8)
=1+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8
=1-1/8
=7/8
② 5/4-9/20+11/30-13/42+15/56
=(1+1/4))-(1/4+1/5)+(1/5+1/6)-(1/6+1/7)+(1/7+1/8)
=1+1/4-1/4-1/5+1/5+1/6-1/6-1/7+1/7+1/8
=1+1/8
=9/8