Find an equation for the nth term of a geometric sequence where the second and fifth terms are -21 and 567, respectively.

an = 7 • (-3)n + 1

an = 7 • 3n - 1

an = 7 • (-3)n - 1

an = 7 • 3n

Question

Find an equation for the nth term of a geometric sequence where the second and fifth terms are -21 and 567, respectively.

 an = 7 • (-3)n + 1

 an = 7 • 3n - 1

 an = 7 • (-3)n - 1

 an = 7 • 3n

mayaal · Answer

@superhelp101  @aryandecoolest  @Moo_Moo17

anonymous · Answer

$$a _{n}= a _{1}r ^{n-1}$$ 
you know this formula?

anonymous · Answer

$$a _{2}= a _{1} r ^{2-1}=-21$$
$$a _{5}=a _{1}r ^{5-1}=567$$

anonymous · Answer

Now solve for $$a _{1}$$ and then substitute in above equation to get value of r

mayaal · Answer

thnku soooo much!!!!

anonymous · Answer

oh! you got it...great!! np) @mayaal