the sum of first n terms of an ap is 5n^2+3n find n terms and 15th term of this ap
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Answer:
Step-by-step explanation:
Sn = 5n2 - 3n an = Sn - Sn - 1
an = 5n2 - 3n - [5(n - 1)2 - 3 (n - 1)]
an = 5n2 - 3n -[5(n2 - 2n + 1) - 3n + 3]
an = 5n2 - 3n - 5n2 + 10n - 5 + 3n - 3
an = 10n - 8
a1 = 2
a2 = 20 - 8 = 12
a3 = 30 - 8 = 22
a16 = 160-8= 152
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By these way, you get the value
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