4) \(=\dfrac{\sqrt{x}-3+\sqrt{x}+3-6}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}=\dfrac{2\left(\sqrt{x}-3\right)}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}=\dfrac{2}{\sqrt{x}+3}\)
5) \(=\dfrac{\sqrt{x}+2+\sqrt{x}-2}{x-4}.\dfrac{x-4}{x+4}=\dfrac{2\sqrt{x}}{x+4}\)
6) \(=\left(5+\dfrac{\sqrt{7}\left(1-\sqrt{7}\right)}{1-\sqrt{7}}\right)\left(5-\dfrac{\sqrt{7}\left(1+\sqrt{7}\right)}{1+\sqrt{7}}\right)=\left(5+\sqrt{7}\right)\left(5-\sqrt{7}\right)=25-7=18\)
Đúng 1
Bình luận (0)
