Question

Pada suatu barisan aritmatika , suku ke-5 =37
dan suku ke-8=19 .jumlah 60 suku barisan tersebut adalah?

Answer 1

B = up-uq / p-q
= 37-19 / 5-8
= 18/-3
= -6

A => Un = a + (n-1) . B
37 = a + (5-1) . -6
37 = a + 4. -6
37 = a + (-24)
37 = a-24
37+24 = a
A = 61

S60 = n/2 (2a + (n-1) .b)
= 60/2 . ( 2.61 + (60-1 ) . -6 )
= 60/2 . ( 122 + 59.-6 )
= 60/2 . (122 + (-354)
= 60/2 . (122 - 354 )
= 60/2 . -232
60. -116
= 6960



Klo ada yg salah maaf ;)