Question

Wyraz ogolny ciagu (bn) ma postac bn=1/2n-1 gdzie n nalezy do N+++
A.bn+1-bn=- 1/2n(2n-1)
B.bn+1-bn=1
C.bn+1-bn=0
D.bn+1-bn=-2/4n2-1

Answer 1

Bn+1=1/2(n+1)-1=1/2n+2-1=1/2n+1
bn=1/2n-1
bn+1-bn=1/2n+1 - 1/2n-1 = 2n-1/(2n+1)(2n-1) - 2n+1/(2n+1)(2n-1) = 2n-1-2n-1/4n2-1  = -2/4n2-1

odp D