Question 1087018
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{{{a[5]}}} = {{{a[1]+4*d}}} = -4 + 4*d = 16  ====>  4d = 20  ===>  d = 5.


The formula is {{{a[n]}}} = -4 + 5*(n-1) = -4 +5n - 5 = -9 + 5n,  n = 1, 2, 3, . . . 


<U>Answer</U>. The general formula is  {{{a[n]}}} = -4 + 5*(n-1)  or  (which is the same)  {{{a[n]}}} =  -9 + 5n,  n = 1, 2, 3, . . .
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