1+ 1/3-7/12+9/20-11/30+13/40-15/56= 1 + 1/3 - 1/3 - 1/4 + 1/4 + 1/5 - 1/5 - 1/6 + 1/6 + 1/7 - 1/7 - 1/8 = 1 - 1/8= 7/8 原式=1/(1×4)+1/(4×7)+1/(7×10)+1/(10×13)+1/(13×16)=1/3×(1/1-1/4+1/4-1/.7+1/7...