Jawabanmu

2014-04-06T07:43:50+07:00
diket: Un=104,a=4,b=9-4=5
Un  = a + (n - 1)b
104 = 4 + (n - 1)5
104 = 4 + 5n - 5
104 =5n - 1
104 + 1 = 5n
105 = 5n
n = 105/5
n = 21


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