Plug n = 1 into the original formula to get an = 14 - 9n a1 = 14 - 9*1 a1 = 5 So the first term is 5
The common difference is -9 as this is the slope in front of the n term. This means each term is going down by 9 each time. Notice the second term is an = 14-9n a2 = 14-9*2 a2 = -4 and so on...
To get the nth term, we subtract 9 from the (n-1)st term That's the same as saying [tex]a_n = a_{n-1}-9[/tex]
So all together, the rule is [tex]a_n = a_{n-1} - 9\\ a_1 = 5[/tex]
