+980 The product of the first and the third terms of an arithmetic sequence is 5. If all terms of the sequence are positive integers, what is the fourth term?
+37146 What positive integers multiply to 5 ?
1 and 5 only so a1 = 1 and a3 = 5
a1 + 2d = 5
1 +2d = 5
d =2 1 3 5 7
