Multiplication
The important rule of multiplication is:
$\text{factor} \cdot \text{factor}$ $=\text{product}$At multiplication, the operands are designated as factor. The product is the result.
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The sign
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If both factors have the same sign the product is positive:
$\color{green}{+} \cdot \color{green}{+} = \color{green}{+}$
$\color{red}{-} \cdot \color{red}{-} = \color{green}{+}$ -
If the factors have different signs the product is negative:
$\color{green}{+} \cdot \color{red}{-} = \color{red}{-}$
$\color{red}{-} \cdot \color{green}{+} = \color{red}{-}$
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Mathematical laws
If $a$, $b$ and $c$ are rational numbers, you have to consider these following mathematical laws:
- Commutative law: $a\cdot b=b \cdot a$
- Associative law: $a\cdot(b \cdot c)=(a \cdot b)\cdot c$ $=a\cdot b \cdot c$