Why does |x + 3| = -6 have no real solutions?

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mathdad
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Explain why there are no real numbers that
satisfy the equation | x + 3 | = - 6.

I know the reason is because of the negative number. Why is this the case?
 
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Let's look at a definition:

$$|u|=\begin{cases}u, & 0\le u \\[3pt] -u, & u<0 \\ \end{cases}$$

Can you see that we must have:

$$0\le|u|$$ ?
 
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