The nth term of an AP is 3+2n. What is the sum of its first seven terms
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0
Answer:
77
step by step explanation :-
a 1 = 3+2(1) =5
a2 = 3+2(2) = 7
a3 = 3+2(3) =9
AP : 5,7,9,...
d = a2 - a1 = 7 - 5 = 2
Sn = n/2 [ 2a + (n-1)d ]
S7 = 7/2 [ 2×5 + (7-1) × 2]
= 7/2 [ 10 + 6×2 ]
= 7/2 [ 10+12 ]
= 7/2 [ 22 ]
= 7×11
77
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the sum of its first seven terms is 77
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