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Nerd ParadiseArtisanal tutorials since 1999

Given: 1 = 1, since that's obvious

1 = √1

1 = √(-1 × -1)

1 = √(-1) × √(-1)

1 = i × i

1 = i2

1 = -1

Q.E.D.

Answer (highlight):

Remember, square root gives TWO answers. Certain rules have to be followed when you break up the radical like that. This is an example of how NOT to do it.