Question

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The sum of n terms of an AP is 3n²+5n.Find the AP and it's 15th term.​

Answer 1

hope this helps you☺️

Answer 2

Answer:

Step-by-step explanation:

Sn = 3n^2 + 5n

Sn – 1 = 3(n – 1)^2 + 5(n – 1)

= 3(n^2 + 1 – 2n) + 5n – 5

= 3n^2 + 3 – 6n + 5n – 5

= 3n^2 – n – 2

an = Sn – Sn – 1 = 3n^2 + 5n – (3n^2 – n – 2)

= 6n + 2

AP is 8, 14, 20, ....................

a(16) => a + 15d = 8 + 15(6) = 98