4. Simplify: $2 \sqrt{1.5+\sqrt{2}}-(1.5+\sqrt{2})$.
Solution:
$1 / 2$

The given expression equals $\sqrt{6+4 \sqrt{2}}-(1.5+\sqrt{2})=\sqrt{6+2 \sqrt{8}}-(1.5+\sqrt{2})$. But on inspection, we see that $(\sqrt{2}+\sqrt{4})^{2}=6+2 \sqrt{8}$, so the answer is $(\sqrt{2}+\sqrt{4})-(1.5+\sqrt{2})=$ $2-3 / 2=1 / 2$