Given a=7,A13=35,find d and S13
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d = 7/3, Sn=273
Step-by-step explanation:
First term of an AP = a = 7
Thirteenth term of an AP = 35
a + 12d = 35 ------(1)
Substitute a in eq - (1)
a + 12d = 35
(7) + 12d = 35
12d = 35 - 7
12d = 28
d = 28/12
d = 7/3
In an AP sum of the terms = n/2 ( a + an )
= 13/2 ( 7 + 35)
= 13/2 ( 42)
= 13(21)
= 273
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