Tentukan jumlah 10 suku pertama pada deret aritmetika 1 1/2 + 2 + 2 1/2...+?

a = 1 1/2
b =;2 - 1 1/2 = 1/2

Sn = 1/2 n (2a + (n-1)b)
S10 = 1/2 x 10 ((2x1 1/2) +(10-1)x 1/2)
= 5 x (3+9/2)
= 5 x 15/2
= 75/2
= 37 1/2

Un = a + (n - 1)b
Un = 1 1/2 + (n - 1)1/2
Un = 3/2 + n/2 - 1/2
Un = 2/2 + n/2
Un = 1+ n/2

Sn = n/2 (a + Un)
S10 = 10/2 [1 1/2 + (1 + 10/2)]
S10 = 10/2 (3/2 + 2/2 + 10/2)
S10 = 10/2 × 15/2
S10 = 150/4
S10 = 75/2
S10 = 37 1/2