Imaginary Numbers
An Imaginary Number, when squared, gives a negative result. |
Try
Let's try squaring some numbers to see if we can get a negative result:- 2 × 2 = 4
- (−2) × (−2) = 4 (because a negative times a negative gives a positive)
- 0 × 0 = 0
- 0.1 × 0.1 = 0.01
It seems like we cannot multiply a number by itself to get a negative answer ...
... but imagine that there is such a number (call it i for imaginary) that could do this:
i × i = −1
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Which means that i is the answer to the square root of −1. |
... by simply accepting that i exists we can solve things
that need the square root of a negative number.
that need the square root of a negative number.
Example: What is the square root of −9 ?
Answer: = √(9 × −1) = √(9) × √(−1) = 3 × √(−1) = 3i(see how to simplify square roots)
In general:
√(−x) = i√x
So long as we keep that little "i" there to remind us that we still
need to multiply by √−1 we are safe to continue with our solution!
Using i we can also come up with new solutions:need to multiply by √−1 we are safe to continue with our solution!
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