Pertanyaan
Suatu barisan aritmatika diketahui suku ke-5 = 37 dan suku ke-8 = 19. Jumlah 20 suku pertama adalah ... ( pakai cara )
Ditanyakan oleh: USER8181
122 Dilihat
122 Jawaban
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Jawaban (122)
u5 = a+4b = 37
u8 = a + 7b = 19
eliminasi
3b = 18
b = 6
a+4(6)=37
a=13
s20= 20/2 (2(13) + (20-1)(6))
10 (26+ 19.6)
10 (26+ 114)
10(140)
1400
u8 = a + 7b = 19
eliminasi
3b = 18
b = 6
a+4(6)=37
a=13
s20= 20/2 (2(13) + (20-1)(6))
10 (26+ 19.6)
10 (26+ 114)
10(140)
1400
Diket :
U5=37
U8=19
Tanya = U20?
U5 = a + (n-1)b
37 = a + 4b
U8 = a + (n-1)b
19 = a + 7b
37 = a +4b
19 = a + 7b
__________-
18 = -3b
-6 = b
19 = a + 7b
19 = a + 7 . (-6)
19 = a - 42
61 = a
U20 = a + (n-1)b
= 61 + 19 . (-6)
= 61 - 114
= -53
U5=37
U8=19
Tanya = U20?
U5 = a + (n-1)b
37 = a + 4b
U8 = a + (n-1)b
19 = a + 7b
37 = a +4b
19 = a + 7b
__________-
18 = -3b
-6 = b
19 = a + 7b
19 = a + 7 . (-6)
19 = a - 42
61 = a
U20 = a + (n-1)b
= 61 + 19 . (-6)
= 61 - 114
= -53