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rnih terrn ofan Đ.Đ. is (2n+] ), what is the nmof its tirst three terms? |
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Answer» The sum of n terms in an AP is given bys= n/2(2a+(n-1)d)wheres = sum of progressionn = number of termsa = value of first termd = difference between 2 terms now, the first term in your question is 3 (2 x 1 + 1)so, a = 3second term is 5 third is 7, like that so d = 2 Therefore, the sum of first n terms of the AP will be n/2 [2 x 3 + (n-1) 2]simplifying, we get the sum as n [3+n-1] n (n+2)Hencen=33(3+2)=3*5=15 |
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