Dik barisan aritmetika

A.
a = -8
b = -5 – (-8)
b = -5 + 8
b = 3

Un = a + (n – 1)b
73 = -8 + (n – 1) × 3
73 = – 8 + 3n – 3
73 = 3n – 11
3n = 73 + 11
3n = 84
n = 84/3
n = 28
Jadi banyak suku barisan tersebut adalah 28 suku

B.
Sn = 1/2(n)[2a + (n – 1)b]
S28 = 1/2(28)[2(-8) + (28 – 1)×3]
S28 = 14[-16 + 27 × 3]
S28 = 14[-16 + 81]
S28 = 14 × 65
S28 = 910
Jadi jumlah keseluruhan barisan tersebut adalah 910

A. Un = a + (n-1)b
73 = -8 + (n-1) 3
73 = -8 + 3n – 3
73 = -11 + 3n
73 + 11 = 3n
84 = 3n
84/3 = n
n = 28

b. Sn = 1/2n (2a + (n-1)b)
S28 = 1/2.28 (2.(-8) + (28-1)3) = 14 (-16 + 27.3) = 14 ( -16 + 81) = 14 (65) = 910