What we want to draw is the half closed interval:
I= [-5, 4) excluding 0,
as the union of 2 different intervals say a and b.
Let a be the interval containing the smallest value.
Then the smallest value of a is -5, and the largest possible value of a is 0, not included, if we want to write a as an interval, without "gaps", or "holes".
So a=[-5, 0)
similarly, b=(0, 4).
Answer: [-5, 4)=[-5, 0)∪(0, 4)
