Consider the absolute values (the numerical values ignoring the signs) of the two numbers. If these are equal then the sum is equal; otherwise the sum takes the sign of which ever number has the larger absolute value.
Yes, they can.
Most of the time yes, positive or negative whole numbers count as rational numbers. So do positive or negative fractions.
They are the infinite number of rational numbers between 0 and +6
Not at all. The class of "natural" numbers are all positive, but the classes of "real" numbers and "rational" numbers include negative numbers.
It is because of the way in which positive and negative numbers are defined.
Rational numbers can be negative or positive.
It the two rational numbers have different signs, then the answer will be negative, otherwise it will be positive.
No, not all negative numbers are rational. There are many negative numbers that are irrational, just like the positive numbers.
Yes. It can also be negative in the numerator. Both positive and negative numbers (as well as zero) can be rational numbers. Both positive and negative numbers can be irrational numbers. Both positive and negative numbers (as well as zero) can be integers.
Yes, they can.
Most of the time yes, positive or negative whole numbers count as rational numbers. So do positive or negative fractions.
Any rational positive number is still rational when you make the same number negative.
They are the infinite number of rational numbers between 0 and +6
Not at all. The class of "natural" numbers are all positive, but the classes of "real" numbers and "rational" numbers include negative numbers.
Yes, they are.
Integers are rational numbers, whether they are positive or negative.
Negative rational numbers are used in the same way that negative whole numbers are used: they are simply the additive inverses of their positive counterparts.