mohon bantuan :) suku ke 5=37 dan suku ke 8=19 pertanyaannya jumlah 60 suku pertama barisan tersebut adalah.. A.708 B.-708 C.-5960 D.-6960

b = U8-U5/ 8-5
= 19-37 /3
= -18/3
=-6
U5 = a+4b
37 = a+4.(-6)
37= a+(-24)
61 =a

Sn = n/2 [2a+(n-1)b]
S60 = 60/2 [2.61+(60-1)-6]
= 30 [ 122+(59.-6)
= 30 (122+(-354)
= 30 (-232)
= - 6960
smoga bermanfaat y,,

U5 = a + 4b = 37
U8 = a + 7b = 18
______________ -
-3b = 18
b = -6

a + 4b = 37
a + 4(-6) = 37
a - 24 = 37
a = 37 + 24
a = 61

S60 = n/2 (2a + 59b)
S60 = 30 (2(61) + 59(-6)
S60 = 30 (122 - 354)
S60 = 30 (-232)
S60 = -6960 (D)

Semoga Membantu