Why don't people understand this basic?
− 1 − 4 = . . .
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2 solutions
Great job, as most other people don't understand that x 2 = ± x , while the truth is x 2 = ∣ x ∣ .
I have answered -2 , too, but actually, the right answer is 2 or -2. Why?
1.- − 1 − 4 = i(2i) = -2
2.- − 1 − 4 = 2 ( − 1 ) ⋅ ( − 4 ) = 2 4 = 2
Furthemore in 1, I can see another little mistake...
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second one is actually the one with mistake.
( a ) ( b ) = ( a b ) DOES NOT APPLY for a , b ∈ ( − ∞ , 0 ) .
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let's suposse you are right, then why you choose i for (-1)^(1/2)? Can't you choose -i?
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@Guillermo Templado – it is a definition. Plus, even if you choose -i, as long as you're consistent with using -i, you will still get -2. SO after all, inconsistence is the one that leads to multiple answers (while there are only 1 right answer).
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@Gian Sanjaya – what is the definition, please?
\[\begin{align} \sqrt{-1} \cdot \sqrt{-4} &= i\sqrt{1} \cdot i\sqrt{4} \\ &= 1i \cdot 2i \\ &= 2i^2 \\ &= 2(-1) \\ &= \boxed{-2}
\end{align}\]
ι × 2 ι = 2 ι 2 As ι 2 = − 1 the value of it becomes − 2 .