Multiply Negative Numbers
How to multiply minus numbers (negative numbers): formula, 3 examples, and their solutions.
Formula
If multiplying same signed numbers,
the result is plus.
(+)⋅(+) = (+)
(-)⋅(-) = (+)
If multiplying different signed numbers,
the result is minus.
(+)⋅(-) = (-)
(-)⋅(+) = (-)
Example-5⋅(-4)
Solution
Solution (Detail)
-5⋅(-4) is (-)⋅(-).
So write (+).
5⋅4 = 20
So +20 is the answer.
Or you can simply write 20.
Example3⋅(-7)
Solution
Solution (Detail)
3⋅(-7) is (+)⋅(-).
So write (-).
3⋅7 = 21
So -21 is the answer.
Example-9⋅2
Solution
Solution (Detail)
-9⋅2 is (-)⋅(+).
So write (-).
9⋅2 = 18
So -18 is the answer.