Answer:
use the formula sn= n(a1+an)/2
Explanation:
2982=28(228+an)/2
5964=28(228+an)
5964/28=228+an
213=228+an
an=-15(last term)
to find difference use formula
an = a+(n-1)d
-15=228+(28-1)d
-243=27d
d=-243/27
d=-9
arithmetic sequence can be found be keep on subtracting 9 from 228
hence the arithmetic sequence is
228, 219, 210, 201, 192, 183, 174........-15