Pertanyaan
Pada barisan aritmatika diketahui U5 = 13 dan U8 = 22 maka nilai suku ke 20 adalah...?
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Ditanyakan oleh: USER6779
149 Dilihat
149 Jawaban
Jawaban (149)
(1)U5=a + 4b = 13
(2)U8=a + 7b = 22
a+4b=13 >a=13-4b
a+7b=22
13-4b+7b=22
13+3b=22
3b=9
b=3
a=13-4(3)
a=13-12
a=1
U20=a+19b
=1+19(3)
=1+57
=58
(2)U8=a + 7b = 22
a+4b=13 >a=13-4b
a+7b=22
13-4b+7b=22
13+3b=22
3b=9
b=3
a=13-4(3)
a=13-12
a=1
U20=a+19b
=1+19(3)
=1+57
=58
U5 = 13 => a+4b = 13
U8 = 22 => a+7b = 22
eliminasi
a+7b = 22
a+4b = 13 -
3b = 9
b = 3
cari nilai a
a+4b = 13
a+4 x 3 = 13
a+12 =13
a = 1
Sn = 1/2 n (2a + (n-1) b)
S20 = 1/2 20 (2x1 + (20-1) 3)
= 10 (2 + 19 x 3)
= 10 (2 + 57)
= 10 x 59
= 590
U8 = 22 => a+7b = 22
eliminasi
a+7b = 22
a+4b = 13 -
3b = 9
b = 3
cari nilai a
a+4b = 13
a+4 x 3 = 13
a+12 =13
a = 1
Sn = 1/2 n (2a + (n-1) b)
S20 = 1/2 20 (2x1 + (20-1) 3)
= 10 (2 + 19 x 3)
= 10 (2 + 57)
= 10 x 59
= 590