in an a.p , an is defined as an = 3+5n,then find sum of first 12 terms
Question
in an a.p , an is defined as an = 3+5n,then find sum of first 12 terms
Solution
The sum of the first n terms of an arithmetic progression can be found using the formula:
S_n = n/2 * (a_1 + a_n)
where: S_n is the sum of the first n terms, n is the number of terms, a_1 is the first term, and a_n is the nth term.
In this case, the nth term a_n = 3 + 5n.
So, the first term a_1 = 3 + 51 = 8 and the 12th term a_12 = 3 + 512 = 63.
Substituting these values into the formula, we get:
S_12 = 12/2 * (8 + 63) = 6 * 71 = 426.
So, the sum of the first 12 terms of the arithmetic progression is 426.
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