In this sequence there are actually two sequences. 1 sequence for the numerators and one sequence for the denominators. The following transformation applies to the sequence for the denominators : +10
This creates the following sequence: [-10, 0, 10, 20, 30, 40, 50]
The following transformation applies to the sequence for the numerators: -5
This creates the following sequence: [9, 4, -1, -6, -11, -16, -21]
Take a good look at how to rewrite the fractions in the series to recognize the pattern.
For example, 0/1 can be rewritten as 0/4