a + d(n-1)
a + d (2) = 1985
a + d(7) = 2015
----------------subtract
0 - 5 d = - 30
d = 6
a + 12 = 1985
a = 1973
1973 + 6(14) = 2057
what is the 15th term of an arithmetic sequence in which the third term is 1985 and the eighth term in 2015?
1 answer
1 answer