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Just wondering, it's been a long time since high school math for me. The the expression below make sense?

I have my doubts because I remember the laws of radicals saying something about division that contradicts the below.

$$ \sqrt{x} \cdot \sqrt{z/w} = \sqrt{(xz)/w} $$

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could always be both. – Will Jagy Apr 12 '12 at 21:47

It's correct if $x$ and $z$ are non-negative and $w$ is positive.

If $a,b \ge 0$ then $\sqrt{a}\sqrt{b}= \sqrt{ab}$.

If $w\ne 0$, then $x\cdot\dfrac z w = \dfrac{xz}{w}$.

You're using those two facts.

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