hitunglah jumlah deret aritmatika nya mohon bantuannya

Jawaban
¶ a = ⅓
¶ b = ½ - ⅓ = 1/6

Maka jumlah deretnys adalah

[tex]sn = \frac{1}{2} n(2a + (n - 1)b) \\ sn = \frac{1}{2} \times 11(2( \frac{1}{3} ) + (11 - 1) \frac{1}{6} ) \\ sn = \frac{1}{2} \times 11( \frac{2}{3} + (10 \times \frac{1}{6} )) \\ sn = \frac{1}{2} \times 11( \frac{2}{3} + \frac{10}{6} ) \\ sn = \frac{1}{2} \times 11( \frac{4 + 10}{6} ) \\ sn = \frac{1}{2} \times 11( \frac{7}{3} ) \\ sn = \frac{1}{2} \times \frac{77}{3} \\ sn = \frac{77}{6} [/tex]