Any listings below are tentative and not intended to be taken as otherwise.
Earth 911
A Summary of Rules for Integers
(Actually, for arithmetic with all rational numbers¡K)
We want to eliminate subtraction much of the time by using the additive
inverse process where we change the subtraction symbol to addition AND
reverse the sign of the number immediately following.
Ex. 5-7 would be 5+(-7)
Addition
If the signs (positive and/or negative) are the same then the sum will carry
the same
sign.
Ex. +2+(+3)=5
-5+(-7) =-12
If the signs are not the same, we must look to the absolute value of
each number (that is to say, the
distance from 0 on a number line). The sum will carry the
sign of the number with the
greater absolute value. The just find the difference.
Ex. 6+(-8)
6 has an absolute value of six; -8 has an absolute value of
8 so the sum will be negative
The difference is 2 so the sum is -2
Multiplication/division
If both factors are either positive or both factors are negative,
then the product (same for division).
is positive.
If one factor is positive and one is negative (same for division),
then the product is negative.
