Answer:
C; B
Step-by-step explanation:
The direct/explicit formula for a geometric sequence is the following:
[tex]a_n=a(r)^{n-1}[/tex]
Where aₙ represents the term n, a represents the initial value, and r represents the common ratio.
Therefore, to find the nth term, we just need to find the initial value and the common ratio.
1)
-8, 24, -72, 216...
The common ratio is the ratio between each consecutive term. Do two to confirm that they are indeed the same. Thus:
[tex]r=24/-8=-3\\r=-72/24\stackrel{\checkmark}{=}-3[/tex]
So, the common ratio is -3. And the initial value is -8. Thus, putting them into our equation:
[tex]a_n=-8(-3)^{n-1}[/tex]
Thus, the eighth term will be:
[tex]a_8=-8(-3)^{8-1}\\a_8=-8(-3)^7\\a_8=17496[/tex]
C
2)
Again, find the common ratio.
2, -14, 98, -686...
[tex]-14/2=-7\\98/-14\stackrel{\checkmark}{=}-7[/tex]
The common ratio is -7. The initial value is 2. Thus:
[tex]a_n=2(-7)^{n-1}[/tex]
And the sixth term will be:
[tex]a_6=2(-7)^{6-1}\\a_6=2(-7)^5\\a_6=-33614[/tex]
B
