jumlah 20 suku pertama baris : 162 + 158 + 154 + 150 + ... adalah...
Matematika
fannyprakoso
Pertanyaan
jumlah 20 suku pertama baris : 162 + 158 + 154 + 150 + ... adalah...
2 Jawaban
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1. Jawaban newwiguna
U20 = a + 19b = 162 + 19(-4) = 162 - 76 = 86
Sn = n/2 x (a+Un)
S20 = 20/2 x (162 + 86)
S20 = 10 x 248
S20 = 2.480 -
2. Jawaban KayrallaKay
a = 162
b = U2-U1 = 158-162 = -4
n = 20
Sn = n/2 (2a + (n-1) b)
S20 = 20/2 (2(162) + (20-1) -4)
S20 = 10 ( 324 + 19 x -4)
S20 = 10 (324 - 76)
S20 = 10 ( 248 )
S20 = 2.480