Question 980023
(x-4),(4-x),x must have equal differences between them

Difference between first and second is (4-x)-(x-4)=4-2x+4=8-2x

The difference between second and third must equal 8-2x.  It is x-(4-x)=2x-4

Therefore, 8-2x=2x-4
12=4x by adding 2x and 4 to both sides;
x=3  ANSWER
-1, 1, 3 are the numbers, and they form an arithmetic progression with difference 2 between each.