Question

1/1*3+1/3*5+1/5*7+.....+1/(2n-1)(2n+1)的值为17/35怎么算

苦求

Answer 1

不可能吧，n值没有给出，1/1*3+1/3*5+1/5*7+.....+1/(2n-1)(2n+1)=1/2(1-1/(2n+1)).如果是17/35，那n=17的

Answer 2

是求N 么？
1/1×3+1/3×5+1/5×7+…+1/(2n-1)(2n+1)
=1/2(1-1/3+1/3-1/5+1/5-1/7+......+1/2n-1-1/2n+1)
=1/2(1-1/2n+1)
=1/2(2n+1-1/2n+1)
=n/2n+1=17/35
35n=17(2n+1)
35n=34n+17
n=17