U3 = 14
U7 = 26
a] Beda suku barisan
U7 - U3 = 26 - 14
7b - 3b = 12
4b = 12
b = 12 / 4
b = 3
b] Suku pertama
a + 2b = 14
a + 2(3) = 14
a + 6 = 14
a = 14 - 6
a = 8
c] Jumlah 18 suku pertama
Sn = n/2 [2a + (n - 1)b]
S18 = 18/2 [2(6) + 17(3)]
S18 = 9 [12 + 51]
S18 = 9 x 63
S18 = 567 ✔
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U3 = 14
U7 = 26
a] Beda suku barisan
U7 - U3 = 26 - 14
7b - 3b = 12
4b = 12
b = 12 / 4
b = 3
b] Suku pertama
U3 = 14
a + 2b = 14
a + 2(3) = 14
a + 6 = 14
a = 14 - 6
a = 8
c] Jumlah 18 suku pertama
Sn = n/2 [2a + (n - 1)b]
S18 = 18/2 [2(6) + 17(3)]
S18 = 9 [12 + 51]
S18 = 9 x 63
S18 = 567 ✔