Series and sequences

Question

Suppose that (b_n) is a sequence of real numbers such that:

(b_n) = (17, -21, 4, -2, 1...) and lim of b_n as n approaches ∞ equals 4

Find s = ∞ ∑ n=1 (b_(n+1) − b_(n))

If the series does not converge, enter 'DNE'.

s=

for clarification: b_n = b subscript n

Answer 1

The sum of differences is -b₁, i.e. -17

because all the terms in the sum of differences add out except for b₁