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anonymous
 one year ago
Find S10 for 2 + 5 + 8 +...
@mathstudent55 i got 270, is that right?
anonymous
 one year ago
Find S10 for 2 + 5 + 8 +... @mathstudent55 i got 270, is that right?

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zzr0ck3r
 one year ago
Best ResponseYou've already chosen the best response.0\(\sum_{n=1}^{10}(2+3(n1))=\sum_{n=1}^{10}1+3n=\sum_{n=1}^{10}1+3\sum_{n=1}^{10}n=10+3\dfrac{10*11}{2}=\\10+3*5*11=16510=155\)

mathstudent55
 one year ago
Best ResponseYou've already chosen the best response.0\(a_1 = 2\), \(a_2 = 5\), and \(a_3 = 8\) We are dealing with an arithmetic series. \(d = a_2  a_1 = 5  2 = 3\) \(a_n = a_1 + (n  1)d\) \(a_{10} = 2 + (10  1)3 = 2 + 9(3) = 29\) \(S_n = \dfrac{n(a_1 + a_n)}{2} \) \(S_n = \dfrac{10(2 + 29)}{2} = 155\)
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