Answer:
See below
Explanation:
Formula
The general term we will use is
t = a r^(n - 1)
Givens
a = - 2
r = - 5
n = 11
t_n = a*r^(n - 1)
t_n = -2*(-5)^(11 - 1)
t_11 = -2*(-5)^10
t_11 = -2 (9,765,625)
t_11 = 19,531,250
Note
Before accepting this answer, you should check to see that the formula works with a value you know the answer to.
t_3 = -2(-5)^(3-1)
t_3 = -2(-5)^2
t_3 = -2 * 25
t_3 = - 50
Which is what your series shows.