Page 44 - Math Smart - 7

Subtraction with negative integers

Example 5

Work out -1-2.
On the number line, we start at -1 and move 2 units to the left.
To subtract a negative
integer, you move to
the left on a horizontal
number line.
-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10
So, -1 -2 = -3.
We can also use number discs to help us.

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So, -1 - 2 is the same as -1 + (-2) = -3.

Example 6

Work out 3-6.
On the number line, we start at 3 and move 6 steps to the left.

-10 -9 -8 -7 -6 -S -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10

We land on -3. So, 3-6 = -3.
We can also use the number discs to help us.

^ (^^) (-1

After arranging to find the zero pairs, we have:

We are left with
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So, 3 - 6 is -3.

UNIT 2 I Integers