pada suatu aritmetika, u5=37 dan u8= 19 jumlah 60 suku pertama barisan trsbt adalah.. A. -5,965 B. 708 C. -708 D. -6,960

U8 = a + 7b = 19
U5 = a + 4b = 37 (dikurang
3b = -18
b = -6
a + 4(-6) = 37
a = 37 + 24
a = 61
S60 = 60/2 (2(61) + 59(-6))
S60 = 30 (122 - 354)
S60 = 30 (-232)
S60 = -6.960

Maaf kalau salah

U5 = 37 U8 = 19
a + 4b = 37 a +7b = 19

a + 4b = 37
a + 7b = 19
Dikurangi jadi -3b = 18
b = -6
a + 4(-6) = 37
a = 37+24=61

S60 = 60/2 (2×61 + 59×(-6))
= 30 (122-354)
= 30 × (-232) = - 6.960 (D)