Alternative proof for multiply two negatives

Question

Many books explain it because you can solve it with addition. I'm interested, is there another way to prove it?

Answer 1

When you multiply two numbers together that are negative, the product is positive.  This is because two negatives make a positive.

 

Suppose I told you "I do not know no better".  The negatives in the sentence are not and no.  So I am actually saying "I do know better".

 

As for addition and subtraction.  Adding a negative number is the same as subtracting that number. Subtracting a negative number is the same as adding that number.  For example.

 

5 + (-3) = 5 - 3

 

5 - (-3) = 5 + 3

 

 

Using a number line can help you to understand adding and subtracting negative numbers.