# How do you simplify 126sqrt2?

$126 \sqrt{2} \approx 36.77$
There is no "simplification" for $126 \sqrt{2}$ (at least not in the sense I assume you were hoping for).
The best you can do is use a calculator to find an approximation for $\sqrt{2}$ (it is $\approx 1.4142$) and multiply that by $126$ to get the answer above.