“A negative times a negative equals…”
Let’s think back to positive integers….
3
3
3
3
+
+
+
=
12
Four groups of positive 3
4 x
3
=
12
4
(3)
=
12
A positive
number
Multiplied by
a positive
A positive
number
What about a group of negative integers….
-3
-3
-3
-3
+
+
+
=
-12
Four groups of negative 3
4 x
-3
=
-12
4
(-3)
=
-12
A positive
number
Multiplied by
a negative
A negative
number
Number lines make sense too….
3
Four groups of positive 3
4 x
3
=
12
-3
=
-12
3
3
3
Four groups of positive 3
4 x
3
=
12
Four groups of negative 3
4 x
-3
-3
=
-12
4 x
-3
-3
-3
4 x
3
=
12
4 x
-3
=
-12
-4 x
-3
=
12
3
2
1
0
-1
-2
-3
-4
4 x
-3
=
-12
-4 x
-3
=
12
4
(-3)
=
-12
(-3)
Patterning can
show WHY...
=
-9
=
-6
=
-3
=
0
=
3
(-3)
(-3)
(-3)
(-3)
(-3)
(-3)
(-3)
=
6
=
9
=
12
add 3
add 3
add 3
add 3
add 3
add 3
add 3
add 3
So what’s
the pattern?
The “switch” on a number line also explains WHY...