Common Core Standard 7ns.2.b
Help, when I multiply or divide positive and negative integers I don’t know if the answer is positive or negative.
Fortunately there are rules to help with this. Two quick and easy ways to remember the rules.
Method 1
Negatives always come in pairs.
Method 2
” Same signs = positive “
“Different signs = negative”
Here are a few examples of multiplying positive and negative numbers.
-4×5= -20
5 x -2= -10
-8x-3 = 24
Multiplying a negative number by zero
Whenever you multiply a number by zero your answer will be zero. Regardless if the number is positive or negative, the answer is zero.
For example:
3 x0 = 0
-5 x 0 = 0
-456 x 0 =0
Multiplying negative numbers and exponents
Whenever you have a negative base and an exponent you need to be on the lookout for parenthesis.
If you have a negative base and parenthesis, the parenthesis applies to the base. An example will help.
( -6^2) = -6 * -6 =36
compare this to
-6^2 = -6 * 6 = -36
-4^2 = -4*4= -16
compare this to
(-4^2) = -4 * -4 = 16
Remember
**Same signs = Positive
Different signs = Negative
Multiplying Negative Numbers and Fractions
Remember our rules for multiplying positive and negative numbers?
These same rules apply to fractions. For example:
(-1/6) * 2/3 = -2/18 = -1/9
(-1/6) * (-2/3) = 1/9
1/6 * 2/3 = 1/9
** Negatives come in pairs
