解法：
原式=9+1/3-49/12+63/20-77/30+91/42-105/56
=9+1/3-49(1/3-1/4)+63(1/4-1/5)-77(1/5-1/6)+91(1/6-1/7)-105(1/7-1/8)
=9+1/3-49/3+49/4+63/4-63/5-77/5+77/6+91/6-91/7-105/7+105/8
=9-48/3+112/4-140/5+168/6-196/7+105/8
=9-16+28-28+28-28+105/8=49/8