Answer:
[tex]U_n=5(-2)^{n-1}[/tex]
Step-by-step explanation:
Given a geometric sequence, the nth term of the geometric sequence is obtained by using the formula:
[tex]U_n=ar^{n-1}[/tex]
If the eleventh term, [tex]a_{11}=5120[/tex]
and the common ratio, r=-2.
Then:
[tex]5120=a(-2)^{11-1}\\a=\frac{5120}{2^{10}} =5[/tex]
The explicit formula for the sequence is:
[tex]U_n=5(-2)^{n-1}[/tex]
