The answer is 4. You take 2 and divide it by 0.5.
An <em>imaginary number</em>. The defining property of an imaginary number is that has the number i attached to it, where i² = -1.
A few examples of imaginary numbers: 3i, i, -7i, (√3)i, (1/2)i
The arithmetic sequence is x - 85 for each one.
170 - 85 = 85
85 - 85 = 0
0 - 85 = -85
and so on
so you subtract 85 each time
hope this helps