Hi!
we know that ak = k if k is odd.
(1)
If n is odd, then an = n and an is positive.
Since statements (1) and (2) mean the same, we should eliminate answers A, B and C.
The formula for sum of the terms in the sequence:
S = 0.5n(a1 + an)
if k = 1, then a1 = 1
n is odd, so an = n
S = 0.5n(1 + n)
We know that n is positive, so S is also positive.
We should eliminate answer E and choose answer D.
Hope it helps!
Best,
Maciek
"There is no greater wealth in a nation than that of being made up of learned citizens." Pope John Paul II
if you have any questions, send me a private message!
should you find this post useful, please click on "thanks" button
