Answer:
4) a₁₅ = 128
5) B. [tex]a_n=a_{n-1}+6[/tex]
Step-by-step explanation:
4)
This is an arithmetic sequence, where all terms have a common difference:
[tex]a_n=a_1+(n-1)d[/tex]
Here, the common difference is 9.
[tex]11-2=9\\20-11=9[/tex]
Use that to write the equation and solve for a₁₅:
[tex]a_n=2+(n-1)9\\\\a_{15}=2+(15-1)9\\a_{15}=2+(14)9\\a_{15}=2+126\\a_{15}=128[/tex]
5)
This is also an arithmetic sequence, but it is a recursive arithmetic sequence in the form of:
[tex]a_n=a_{n-1}+d[/tex]
This simply states that each term is d more than the term before it.
Here, the common difference is 6:
[tex]2--4=6\\8-2=6\\14-8=6[/tex]
And the equation for this is B. [tex]a_n=a_{n-1}+6[/tex]