SOLUTION: Don't understand what is correct way to do this! Question: What's wrong with using product rule for solving equation -4(under radical sign) times -4 (under the radical sign?

Question 44138: Don't understand what is correct way to do this!
Question: What's wrong with using product rule for solving equation -4(under radical sign) times -4 (under the radical sign?
I would say put both under radical and then square to get correct answer of 4. Notes say what is correct product? Hinted that 4 was not it.

Answer by psbhowmick(878) (Show Source): You can put this solution on YOUR website!
is not a real number. So the rule you mentioned is not applicable here.
Such numbers, with -ve sign under the radical, are called imaginery.
is called as the imaginery square root of unity and is denoted by .
So, .
Hence, .
Now, = = = .
Hence, = = = -4

To know more about such problems read chapters on imaginery and complex numbers.
All the laws of Mathematical operation which hold for real numbers are not necessarily true with imaginery numbers.
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