Q. If nth term of an A.P. is (3n+1), what is the sum of its first four terms?
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Hey !!!
nth term = 3n + 1
So, 1st term = 3(1) + 1
= 4....
2nd term
= 3 (2) + 1
= 7....
So,
d is 2nd term - 1st term
= 7 - 4 = 3.....
Hence,
Sum of 4 terms
= 4/2 { 2 * 4 + 3(4 - 1) }
= 2 * 17
= 34
nth term = 3n + 1
So, 1st term = 3(1) + 1
= 4....
2nd term
= 3 (2) + 1
= 7....
So,
d is 2nd term - 1st term
= 7 - 4 = 3.....
Hence,
Sum of 4 terms
= 4/2 { 2 * 4 + 3(4 - 1) }
= 2 * 17
= 34
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