(ü) given a = 7,a13= 35, find d and S13.
Answers
Answered by
1
Answer:
a=7,a13=35.
d=a2-a1,
7+6d=a7
7+12d=35
d=-35/6
s13=n/2(2a+(n-1)*d
s13=13/2(2*7+(n-1)*35/6
Answered by
1
Answer:
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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