Why does multiplying two negative numbers equal a positive number?

Question

Why does multiplying two negative numbers equal a positive number?

In: 1210

Answer 1

Negative number are just regular numbers with the minus sign in front. Lets try using a different sign to show a negative number. Lets use @.

1 is positive
@1 is negative

@1+@1=@2
@1-@1=0
@1-@2=1

Multiplication is just addition

3*4= 3+3+3+3 = 12

@3*4= (@3)+(@3)+(@3)+(@3) = @12

@3*-4= (@3)-(@3)-(@3)-(@3) = 12