Find an equation for the nth term of the sequence.

-4, -16, -64, -256, ...

an = 4 • -4n
an = 4 • -4n + 1
an = -4 • 4n
an = -4 • 4n - 1

Question

Find an equation for the nth term of the sequence.

-4, -16, -64, -256, ...

an = 4 • -4n 
an = 4 • -4n + 1 
an = -4 • 4n 
an = -4 • 4n - 1

hartnn · Answer

could u see any pattern ?

hartnn · Answer

and if you know Geometric sequence,
can you find the common ratio ?

anonymous · Answer

times 4

hartnn · Answer

thats correct!
so the common ratio = r =4 

now the first term = a1 = -4

just plug all these in the general geometric series formula
$\huge a_n = a_1r^{n-1}$

anonymous · Answer

Oh wow that easier that I thought. Thanks!

hartnn · Answer

yes it is easy :)
welcome ^_^