求助题目
(1/(1*4))+(1/(4*7))+(1/(7*10))...+(1/(91*94))
参考答案:(1/(1*4))+(1/(4*7))+(1/(7*10))...+(1/(91*94))
=1/3(1-1/4+1/4-1/7+1/7-1/10+……+1/91-1/94)
=1/3(1-1/94)
=1/3*93/94
=31/94
(1/(1*4))+(1/(4*7))+(1/(7*10))...+(1/(91*94))
参考答案:(1/(1*4))+(1/(4*7))+(1/(7*10))...+(1/(91*94))
=1/3(1-1/4+1/4-1/7+1/7-1/10+……+1/91-1/94)
=1/3(1-1/94)
=1/3*93/94
=31/94