The sum of first 6 terms of an arithmetic
Sequence is 99 and the 6th team is 39.
(a find the sum of x3 and x4
b write the 3rd team
@ write the sequence.
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Step-by-step explanation:
The sum of the first N terms of the arithmetic sequence
is
N*(A1 + An)/2 = SUM
6*(A1 + A6)/2 = 99
6*(A1 + 39)/2 = 99
3(a1+39) = 99
a1 + 39 = 33
a1 = -6
Next for divided difference D, An = a1 + (n-1)*D
39 = -6 + (6-1)*D
39 = -6 + 5*D
45 = 5D
D = 9
The sequence is -6, 3, 12, 21, 30, 39
12+21 = 33
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