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Bogdan [553]
3 years ago
6

Why is -a² is always negative (a ≠ 0) and why is (-a)² is always positive?

Mathematics
1 answer:
hjlf3 years ago
6 0
-a^2=(-1)\cdot a\cdot a

Regardless of the sign of a, we have a\cdot a=a^2\ge0 (never negative). But multiplying by -1 makes it negative.

On the other hand,

(-a)^2=((-1)\cdot a)^2=(-1)^2\cdot a^2=1\cdot a^2=a^2

which can never be negative for real a.
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