Answer:
1. 81
2.238
Step-by-step explanation:
Sn = n/2 [2 a1 + (n-1) d]
Sn= 6/2 [2(1)+ (6-1)5]
= 3 [2 + (5)5]
=3 (2 + 25)
= 3 (27)
= 81
2. Sn 7/2 [2(7) +(7-1)9]
= 7/2 [14 + (6)9]
= 7/2 (14 +54)
= 7/2 (68)
= 238
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Answers & Comments
Answer:
1. 81
2.238
Step-by-step explanation:
Sn = n/2 [2 a1 + (n-1) d]
Sn= 6/2 [2(1)+ (6-1)5]
= 3 [2 + (5)5]
=3 (2 + 25)
= 3 (27)
= 81
2. Sn 7/2 [2(7) +(7-1)9]
= 7/2 [14 + (6)9]
= 7/2 (14 +54)
= 7/2 (68)
= 238