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## Homework Statement

I have a simple problem with roots and absolute values. When is the root of a number both negative and positive? Is only the equation of a number say f(x) = √x both the negative root and the positive root?

## Homework Equations

If a = 1; b = -2, och x = a

^{2}√(ab-b

^{2}+2)

Why is x only 2 and not -2 aswell?

However if it were a function say f(x) the answer would be 2 and -2 right?

Edit: For clarification how come √4 = 2 but f(4) = √4 = 2 and -2

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