数列bn=2^n/(4^n-1),证明b1+b2+b3+……+bn

问题描述:

数列bn=2^n/(4^n-1),证明b1+b2+b3+……+bn

bn=2^n/(4^n-1)b1= 2/3b2 = 4/15b3 = 8/63for n>=4bn =2^n/(4^n-1)