9 , 4 , -1 , -6, -11
As we could noticed, the number is decreasing. And to know the value it decreases, we should subtract the first to the next number.
9 - 4 = 5
4 - (-1) = 5
So It always decreases by 5.
So let's continue,
9, 4, -1, -6, -11, ?, ?, ?
-11 - 5 = -16
So, next to -11, is -16
9, 4, -1, -6, -11, -16, ?, ?
-16 - 5 = -21
So next to -16, is -21
9, 4, -1, -6, -11, -16, -21, ?
-21 - 5 = -26
9, 4, -1, -6, -11, -16, -21, -26
The next number is -16, the 8th number is -26.
