Question

The first term is 9, and the explicit formula is Tn = a + 4(n - 1). Find the 9th term of the sequence.45484157

Answer 1

The first term is given when n=0

$T_0=a+4(0-1)=9\Rightarrow9=a-4\Rightarrow a=13$

The explicit formula is

$T_n=13+4(n-1)$

Note that with n=0 we obtain the first term, which is 9, and the second term is the value of Tn with n=1, which means the 9th term is given by n=8, like this

$T_8=13+4(8-1)=13+4(7)=13+28=41$

Therefore, the 9th term is 41.