# What are the Integer rules????? HELP???

• Jan 23rd 2009, 10:41 AM
ifailatmath
What are the Integer rules????? HELP???
How can you remember integer rules, such as
a negative x a negative = positive
Plus:
what ARE the rules? I don't know!!!! How do you calculate a negative x a positive? WHAT ARE THE RULES??? I FAIL AT MATH!!!!!!
• Jan 23rd 2009, 11:02 AM
Mush
Quote:

Originally Posted by ifailatmath
How can you remember integer rules, such as
a negative x a negative = positive
Plus:
what ARE the rules? I don't know!!!! How do you calculate a negative x a positive? WHAT ARE THE RULES??? I FAIL AT MATH!!!!!!

Let a and b be positive integers:

$\displaystyle a \times b = ab$

$\displaystyle (-a) \times b = (-1) \times a \times b = -ab$

$\displaystyle (-a) \times (-b) = (-1) \times a \times (-1) \times b = (-1)(-1)ab = ab$

$\displaystyle a \times (-b) = a \times (-1) \times b = -ab$

The integers are also closed under addition. Adding an integer to another always gives an integer. Ratios of integers are known as rational numbers. If a divides b, then the ratio a/b is an integer. If a doesn't divide b, then the ratio a/b is a rational number.
• Jan 23rd 2009, 11:12 AM
fetfet