Suatu barisan aritmatika memiliki suku ke -5 = 16 dan suku ke -8 = 22 jumlah 20 suku pertama barisan tersebut adalah

langsung aja y

U5 = a + 4b = 16
U8 = a + 7b = 22
_____________-
-3b = -6
b = 2

a + 4b = 16
a = 16 - 4(2)
a = 16 - 8
a = 8

S20 = 20/2 (2a + 19b)
S20 = 10 ( 2.8 + 19.2)
S20 = 10 ( 16+38)
S20 = 10 (54)
S20 = 540

semoga berguna +_+

b = U8-U5/8-5
= 22-16/3
= 6/3
=2
U5 = a+ 4b
16 = a+8
8 = a

Sn = n/2(2a+(n-1)b)
S20 = 20/2 (16+(19.2)
=10(16+38)
= 10(54)
= 540

smoga membantu