The arithmetic sequence is given by:
[tex]a_n=a_1+(n-1)d[/tex]
Where:
a1 = First term
d = Common difference
Using the data provided:
[tex]\begin{gathered} a_1=11 \\ a_2=12=11+(2-1)d_{} \\ 12=11+d \\ d=12-11 \\ d=1 \end{gathered}[/tex]
Therefore, the explicit formula is:
[tex]\begin{gathered} a_n=11+(n-1)1 \\ a_n=11+n-1 \\ a_n=n+10 \end{gathered}[/tex]
n = 20
[tex]\begin{gathered} a_{20}=20+10 \\ a_{20}=30 \end{gathered}[/tex]
Answer:
[tex]\begin{gathered} a_n=n+10 \\ a_{20}=30_{} \end{gathered}[/tex]
