$4 - 4 = 0$
Ok, the first number is assumed as a positive and the operation here is a subtraction, so the second number is a positive also.
So I can summ it in the same way by specifying the second number as a negative: $4 + (-4) = 0$
If I did the same but making the first number a negative, $-4 + 4$, why is it equal to $0$ and not $-8$?
Why do I have to specify that the second number is a negative also? $-4 + (-4) = -8$
How can I add a number to a negative number without specifying it to be negative?
(I mean, by the same logic of specifying a negative, why don't I need to specify this: $-4 + (+4) = 0$ instead of assuming the one without a specific direction is always a positive?)