Answer:
= 10

Explanation:
Note that consecutive terms have a common ratio, that is
50 ÷ 10 = 250 ÷ 50 = 1250 ÷ 250 = 5
This indicates that the sequence is geometric with n th term ( explicit rule )
= a

where a is the first term and r the common ratio,
Here a = 10 and r = 5, thus
= 10
← explicit rule