Answer:
A; D; A; C; C
Step-by-step explanation:
1. S29 means the sum of the first 29 terms. Because it's an arithmetic sequence, the sum of the first x terms is (the first term + xth term)(x)/2
That means the answer to the first question is (7+70)(29)/2 = 1116.5 (A)
2. The sum of the first 18 terms is (56 + 5)(18)/2 = 549 (D)
3. The common difference is 3.5, making the 26th term 87.5. That makes the sum of the first 26 terms (7+94.5)(26)/2 = 1319.5 (A)
4. The question is asking for the sum of the first 28 terms. The first term is 50-4(1) = 46. The 28th term is 50-4(28) = -62. That makes the sum of the first 28 terms (46+(-62))(28)/2 = -224 (C)
5. The first x terms of a geometric sequence is the (first term - (x+1)th term)/(1-(ratio)).
That makes the sum ((1/3)-(729))/(1-3) = -(2186/3)/-2 = 1093/3 = 364 1/3 (C)
