Question

The sum of first n terms of an AP is given by Sn = 3n+ 10n. Find the nth term of the AP​

Answer 1

ᕼᗩᐯᗴ ᗩ ՏᗯᗴᗴT ᗪᗩY ❤️

ᴄʜᴇᴍɪsᴛʀʏ ᴅᴇғɪɴɪᴛɪᴏɴ, ᴛʜᴇ sᴄɪᴇɴᴄᴇ ᴛʜᴀᴛ ᴅᴇᴀʟs ᴡɪᴛʜ ᴛʜᴇ ᴄᴏᴍᴘᴏsɪᴛɪᴏɴ ᴀɴᴅ ᴘʀᴏᴘᴇʀᴛɪᴇs ᴏғ sᴜʙsᴛᴀɴᴄᴇs ᴀɴᴅ ᴠᴀʀɪᴏᴜs ᴇʟᴇᴍᴇɴᴛᴀʀʏ ғᴏʀᴍs ᴏғ ᴍᴀᴛᴛᴇʀ

Answer 2

Answer:

Sn = 3n^2 + 10n

So, S(n - 1) = 3 (n - 1)^2 + 3(n - 1)

So, An = Sn - S(n - 1) = 3n^2 + 10n - 3(n - 1)^2 - 10(n - 1) = 3n^2 + 10n - 3 ((n^2) - 2n + 1) -10(n - 1) = 3n^2 + 10n - 3n^2 + 6n - 3 - 10n + 10 = 6n + 7

So, n th term of the given sequence is (6n + 7), its first term is 13 and common difference is 6. The common difference is constant. So, the given sequence