Why is -4 x -4 =16?

Why is the product of two negative numbers positive?

Take -4 x -4 = 16 for example. Shouldn't it be -16?

Conjecture:

-4 x -4 = -16

Proof:

-4 x -4 = (-1 x 4) x (-1 x 4)
=-1 x (4 x 4) by distibutive law
=-1 x (16)
=-16

QED

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