1乘2分之1加2乘3分之1加3乘4分之1加4乘5分之1加5乘6分之1加6乘7分之1
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=1-1/7
=6/7
=7分之61-1/7是怎么得来的，你在写下详细的算式OK？1/（1×2）=1-1/21/（2×3）=1/2-1/31/（3*4）=1/3-1/41/（4*5）=1/4-1/51/（5*6）1/5-1/61/（6*7）=1/6-1/7（-1/2+1/2）=0（-1/3+1/3）=0（-1/4+1/4）=0（-1/5+1/5）=0（-1/6+1/6）=0∴1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7=1-1/7=6/7