数列{an}中①Sn=π(2n²+n)/12 ②Sn=2/3(3n-1) 求an
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![数列{an}中①Sn=π(2n²+n)/12 ②Sn=2/3(3n-1) 求an](/uploads/image/z/840157-61-7.jpg?t=%E6%95%B0%E5%88%97%EF%BD%9Ban%EF%BD%9D%E4%B8%AD%E2%91%A0Sn%3D%CF%80%EF%BC%882n%26%23178%3B%2Bn%EF%BC%89%2F12+%E2%91%A1Sn%3D2%2F3%EF%BC%883n-1%EF%BC%89+%E6%B1%82an)
数列{an}中①Sn=π(2n²+n)/12 ②Sn=2/3(3n-1) 求an
数列{an}中①Sn=π(2n²+n)/12 ②Sn=2/3(3n-1) 求an
数列{an}中①Sn=π(2n²+n)/12 ②Sn=2/3(3n-1) 求an
(1)
Sn=π(2n^2+n)/12 (1)
S(n-1)=π(2(n-1)^2+(n-1))/12 (2)
(1)-(2)
an=(π/12)(4n-1)
(2)
Sn=(2/3)(3n-1) (1)
S(n-1)=(2/3)(3(n-1)-1) (2)
(1)-(2)
an =2