# How do you simplify 4/sqrt21? Thank you very much for your help.?

Mar 30, 2015

I don't know if it is much of a simplification but you could rationalize the denominator by multiplying the top and bottom by $\sqrt{21}$

$\frac{4}{\sqrt{21}} = \frac{4 \sqrt{21}}{21}$

As I said, not much of an improvement, but some people prefer to keep roots out of the denominator.
There is no real simplification beyond this.

Mar 30, 2015

I would multiply and divide by $\sqrt{21}$ and get:
$\frac{4}{\sqrt{21}} \cdot \frac{\sqrt{21}}{\sqrt{21}} = 4 \frac{\sqrt{21}}{21} = \frac{\sqrt{336}}{21}$