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HOW TO WORK WITH NEGATIVE NUMBERS

 

Multiplying and Dividing

Memorize these rules:

plus times plus is plus

(+3)(+3) = +9

minus times minus is plus

(-3)(-3) = +9

minus times plus is minus

(-3)(+3) = -9

plus divided by plus is plus

3 ÷ 3 = 1

minus divided by minus is plus

(-3) ÷ (-3) = +1

minus divided by plus is minus

(-3) ÷ (+3) = -1

 

 

Adding and Subtracting

Study this number line:

for plus: count toward the right, for minus: count toward the left

For example, start at -6 and count two spaces in the plus direction. You come to -4. So -6 + 2 = -4.

Here's a different one:  start at -6 and count two in the minus direction. You come to -8. So -6 -2 = -8

 

Now count off these on the number line:

-6 + 8 = +2

-6 - 4 = -10

+4 - 8 = -4

+4 + 2 = +6

 

Here are some tricky ones: remember minus minus is plus:

-6 - (-2) = -6 +2 = -4

4 - (-1) = +5

4 + (-1) = 4 - 1 = +3

-½ + ½ = 0

Also:

-6x + 8x = +2x

-6a - 2a = -8a

-4x2 - (-8x2) = +4x2

 

During exams, use your calculator for all computations with negative numbers.