\(x=7-4\sqrt{3}\\ =>\sqrt{x}=\sqrt{7-4\sqrt{3}}=\sqrt{\left(2-\sqrt{3}\right)^2}=\left|2-\sqrt{3}\right|=2-\sqrt{3}\\ \)
Thay \(\sqrt{x}=2-\sqrt{3}\)
\(A=\dfrac{2-\sqrt{3}+2}{2-\sqrt{3}+3}=\dfrac{4-\sqrt{3}}{5-\sqrt{3}}=\dfrac{\left(4-\sqrt{3}\right)\left(5+\sqrt{3}\right)}{25-3}=\dfrac{20-5\sqrt{3}+4\sqrt{3}-3}{22}=\dfrac{17-\sqrt{3}}{22}\)
kHI X=7-4\(\sqrt{3}\) = 22-2.2.\(\sqrt{3}\)+(\(\sqrt{3}\))2=(2-\(\sqrt{3}\))2
A=\(\dfrac{\sqrt{x}+2}{\sqrt{x}+3}\) <=> A=\(\dfrac{\sqrt{\left(2-\sqrt{3}\right)^2}+2}{\sqrt{\left(2-\sqrt{3}\right)^2}+3}\)=\(\dfrac{2-\sqrt{3}+2}{2-\sqrt{3}+3}\) =\(\dfrac{4-\sqrt{3}}{5-\sqrt{3}}\)
\(x=7-4\sqrt{3}=4-4\sqrt{3}+\left(\sqrt{3}\right)^2=>\sqrt{x}=\sqrt{\left(2-\sqrt{3}\right)^2}=2-\sqrt{3}\left(2>\sqrt{3}\right)\)
\(A=\dfrac{2-\sqrt{3}+2}{2-\sqrt{3}+3}=\dfrac{4-\sqrt{3}}{5-\sqrt{3}}\)
