Sn = 7n² - 3n
n= 1 --> s1 = a= 7-3= 4
b = 2(7) = 14
un = a + (n-1)b
Un = 4 +(n-1)14
Un = 14n - 10
D
Penjelasan dengan langkah-langkah:
step 1
__ __ __
S1 = 7(1)² - 3(1) = 4
S2 = 7(2)² - 3(2) = 22
a = S1 = 4
step 2
S2 = U1 + U2
S2 = a + (a + b)
S2 = 2a + b
22 = 2•4 + b
b = 22 - 8
b = 14
step 3
Un = a + (n - 1)b
Un = 4 + (n - 1)14
Un = 4 + 14n - 14
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Sn = 7n² - 3n
n= 1 --> s1 = a= 7-3= 4
b = 2(7) = 14
un = a + (n-1)b
Un = 4 +(n-1)14
Un = 14n - 10
D
Penjelasan dengan langkah-langkah:
step 1
__ __ __
Sn = 7n² - 3n
S1 = 7(1)² - 3(1) = 4
S2 = 7(2)² - 3(2) = 22
a = S1 = 4
step 2
__ __ __
S2 = U1 + U2
S2 = a + (a + b)
S2 = 2a + b
22 = 2•4 + b
b = 22 - 8
b = 14
step 3
__ __ __
Un = a + (n - 1)b
Un = 4 + (n - 1)14
Un = 4 + 14n - 14
Un = 14n - 10