2/(14)+2/(47)+2/(710)+2/(1013)+...+2/(3n-2)(3n+1)快点,我明天就要交了

来源：学生作业学帮网编辑：学帮网时间：2024/06/05 09:08:47

2/(1*4)+2/(4*7)+2/(7*10)+2/(10*13)+...+2/(3n-2)(3n+1)
快点,我明天就要交了

拆项法原式=2/3(1-1/4+1/4-1/7+1/7.-1/(3n-2)+1/(3n12)-1/(3n+1))=2/3(1-1/(3n+1))=2n/(3n+1)

2/(1*4)+2/(4*7)+2/(7*10)+2/(10*13)+...+2/(3n-2)(3n+1)快点,我明天就要交了