ANSWER:
511
STEP-BY-STEP EXPLANATION:
We have that the sequence is given as follows according to the statement:
[tex]a_n=2\cdot(a_{n-1})+1[/tex]Therefore, to calculate the value of the 9t0 term, we can do the following:
[tex]\begin{gathered} a_{10}=2\cdot a_9+1 \\ a_{10}=1023 \\ \text{ replacing and solve for }a_9\colon \\ 1023=2\cdot a_9+1 \\ 2\cdot a_9=1023-1 \\ a_9=\frac{1022}{2} \\ a_9=511 \end{gathered}[/tex]The 9th term is 511
