\(1,=\dfrac{2+\sqrt{3}+2-\sqrt{3}}{\left(2-\sqrt{3}\right)\left(2+\sqrt{3}\right)}\cdot\dfrac{\sqrt{3}-1}{\sqrt{3}\left(\sqrt{3}-1\right)}=4\cdot\dfrac{1}{\sqrt{3}}=\dfrac{4\sqrt{3}}{3}\\ 2,=\left(\dfrac{\sqrt{2}\left(\sqrt{2}+1\right)}{\sqrt{2}+1}+1\right)\left(\dfrac{\sqrt{2}\left(\sqrt{2}-1\right)}{\sqrt{2}-1}-1\right)\\ =\left(\sqrt{2}+1\right)\left(\sqrt{2}-1\right)=2-1=1\\ 3,A=\dfrac{2}{\left(a-2b\right)\left(a+2b\right)}\cdot\sqrt{\dfrac{\left(a+2b\right)^2}{4}}\\ A=\dfrac{2}{\left(a-2b\right)\left(a+2b\right)}\cdot\dfrac{a+2b}{2}=\dfrac{1}{a-2b}\)
\(4,D=x-4-\sqrt{\left(x-4\right)^2}=x-4-\left|x-4\right|\\ D=x-4-x+4=0\\ 5,=19\sqrt{3a}-12\sqrt{3a}+\dfrac{3\sqrt{5a}}{2}+\dfrac{7\sqrt{3a}}{2}\\ =\dfrac{14\sqrt{3a}+3\sqrt{5a}+7\sqrt{3a}}{2}=\dfrac{21\sqrt{3a}+3\sqrt{5a}}{2}\)
