是一直乘到1001吧?
(1乘3)分之2,加(3乘5)分之2,加(5乘7)分之2,再加加加到(999乘1001)分之2
2/(1×3)+2/(3×5)+2/(5×7)+…+2/(999×1001)
=(1-1/3)+(1/3-1/5)+(1/5-1/7)+…+(1/999-1/1001)
=1-1/1001=1000/1001
解:
2/(1×3)+2/(3×5)+2/(5×7)+…+2/(999×1001)
=(1-1/3)+(1/3-1/5)+(1/5-1/7)+…+(1/999-1/1001)
=1-1/1001=1000/1001