72应该改为701-1/4-1/28-1/70-1/130 =1-1/(1×4)-1/(4×7)-1/(7×10)-1/(10×13)=1-1/3（1-1/4）-1/3（1/4-1/7）1/3（1/7-1/10）-1/3（1/10-1/13）=1-1/3×（1-1/4+1/4-1/7+1/7-1/10+1/10-1/13）=1-1/3×（1-1/13）=...你是青松的?1/10+1/40+1/88+1/154+1/238+1/340裂项法1/10+1/40+1/88+1/154+1/238+1/340=1/2×5+1/5×8+1/8×11+1/11×14+1/14×17+1/17×20=1/3×（1/2-1/5+1/5-1/8+1/8-1/11+1/11-1/14+1/14-1/17+1/17-1/20）=1/3×（1/2-1/20）=1/3×9/20=3/20