Perhatikan barisan bilangan berikut : 5,12,21,32,45 ... Suku ke 14 dari barisan tersebut adalah?

Mapel : Matematika
Materi : Baris dan Deret

5, 12, 21, 32, 45,....a = 5
   7,   9,  11,  13,......b = 7
      2,   2,    2,...........c = 2

[tex]\text{Un}= a+((n-1)\times b)+(\frac{1}{2}\times (n-1)\times(n-2)\times c)\\ \\ \text{Un}= 5+((n-1)\times 7)+(\frac{1}{2}\times (n-1)\times(n-2)\times 2)\\ \\ \text{Un}= 5+7n-7+n^2-3n+2\\ \\ \bold{\text{Un}= n^2+4n}[/tex]

[tex]U_{14} =14^2+(4\times14) \\ \\U_{14} =196+56\\ \\ \bold{U_{14} =252}[/tex]

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