1. Diket : barisan aritmatika -7, -4, -1, 2, 5, ...38
Ditanya : n?
Jawab :
a = -7
b = -7 - (-4) = -3
Un = 38
Un = a + (n-1)b
38 = -7 + (n-1) -3
38 = -7 + (-3n) +3
38 = -4 - 3n
3n = -4 - 38
3n = -42
n = -42/3
n = -14
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1. Diket : barisan aritmatika -7, -4, -1, 2, 5, ...38
Ditanya : n?
Jawab :
a = -7
b = -7 - (-4) = -3
Un = 38
Un = a + (n-1)b
38 = -7 + (n-1) -3
38 = -7 + (-3n) +3
38 = -4 - 3n
3n = -4 - 38
3n = -42
n = -42/3
n = -14