Remember !

The set of integers is the set which contains natural numbers and the negatives of the natual numbers. Integers are used to express values for temperatures, to measure altitudes in respect to the sea level etc.

Integers preceded by the sign (+) are called positive integers while the ones preceded by sign (-) are called negative integers. Is not neccessary to write the sign (+) in front of the positive integers.

In case of numbers with the same sign, we add their absolute values and the result takes the sign. For example, (+a)+(+b)=+(a+b) and (-a)+(-b)=-(a+b). The sum of two opposite integers is 0.

Exemple !

- 2 + 1= -1

-1 + (- 2) = -3

-3 + (-3) = 6