Tentukan rumus suku ke-n dari barisan 7, 3, -1, -5, . . . a. 11 - 2n b. 12 - 4n c. 11 - 4n d. 11 - n e. 11 - 3n
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SOAL 1
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Un = a + (n - 1)b
a = 7
b = -4
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Un = 7 + (n - 1)(-4)
Un = 7 + (n × -4) (-1 × -4)
Un = 7 + (-4n) + 4
Un = 7 - 4n + 4
Un = (7 + 4) - 4n
Un = 11 - 4n
Opsi(C.)
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Penjelasan dengan langkah-langkah:
b = -4
a = 7
maka :
Un = a + (n-1)b
Un = 7 + (n-1)-4
Un = 7 + -4n + 4
Un = 7 + 4 - 4n
Un = 11 - 4n (c)
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