Đặt \(B=\sqrt{9+\sqrt{5}}+\sqrt{9-\sqrt{5}}\)
=>\(B^2=9+\sqrt{5}+9-\sqrt{5}+2\cdot\sqrt{81-5}\)
=>\(B^2=18+2\sqrt{76}\)
=>\(B=\sqrt{18+2\sqrt{76}}\)
\(\Leftrightarrow A=\sqrt{\dfrac{18+2\sqrt{76}}{9+2\sqrt{19}}}-\sqrt{3-2\sqrt{2}}\)
\(=\sqrt{\dfrac{2\left(9+2\sqrt{19}\right)}{9+2\sqrt{19}}}-\sqrt{2}+1=\sqrt{2}-\sqrt{2}+1=1\)
Rút gọn:
a) \(\sqrt{15-6\sqrt{6}}+\sqrt{33-12\sqrt{6}}\)
b) \(\sqrt{\left(3+\sqrt{5}\right)^2}+\sqrt{14-6\sqrt{5}}\)
c) \(\dfrac{3}{2\sqrt{3}+3}+\dfrac{3}{2\sqrt{3}-3}\)
d) \(\sqrt{\left(\sqrt{3}+4\right)\sqrt{19-8\sqrt{3}}+3}\)
e) \(\dfrac{9-2\sqrt{3}}{3\sqrt{6}-2\sqrt{2}}+\dfrac{3}{3+\sqrt{6}}\)
cho x=\(\left(\dfrac{\sqrt[3]{8-3\sqrt{5}}+\sqrt[3]{64-12\sqrt{20}}}{\sqrt[3]{57}}\right)\sqrt[3]{8+3\sqrt{5}}\);y=\(\left(\dfrac{\sqrt[3]{9}-\sqrt{2}}{\sqrt[3]{3}+\sqrt[4]{2}}+\dfrac{\sqrt{2}-9\sqrt[3]{9}}{\sqrt[4]{2}-\sqrt[3]{81}}\right)\)
a rút gọn x và y
b tính T = xy
a) \(\sqrt{4x^2-9}=2\sqrt{x+3}\)
b) \(\sqrt{4x+20}+3\sqrt{\dfrac{x-5}{9}}-\dfrac{1}{3}\sqrt{9x-45}=4\)
c) \(\dfrac{2}{3}\sqrt{9x-9}-\dfrac{1}{4}\sqrt{16x-16}+27\sqrt{\dfrac{x-1}{81}}=4\)
d)\(5\sqrt{\dfrac{9x-27}{25}}-7\sqrt{\dfrac{4x-12}{9}}-7\sqrt{x^2-9}+18\sqrt{\dfrac{9x^2-81}{81}}=0\)
Rút gọn:
A=\(\left(\dfrac{2\sqrt{3}-\sqrt{6}}{\sqrt{8}-2}-\dfrac{\sqrt{216}}{3}\right).\dfrac{1}{\sqrt{6}}\)
B=\(\sqrt{9+4\sqrt{5}}+\sqrt{9-4\sqrt{5}}\)
9) \(\sqrt{20}\) + 2\(\sqrt{45}\) + \(\sqrt{125}\) - 3\(\sqrt{80}\)
10) \(\sqrt{75}\) - \(\sqrt{5\dfrac{1}{3}}\) + \(\dfrac{9}{2}\) \(\sqrt{2\dfrac{2}{3}}\) + 2\(\sqrt{27}\)
Rút gọn
(\(\dfrac{\sqrt{x}}{3+\sqrt{x}}\)+\(\dfrac{2x}{9-x}\)):(\(\dfrac{\sqrt{x}-1}{x-3\sqrt{x}}-\dfrac{2}{\sqrt{x}}\))
(\(\dfrac{\sqrt{x}-2}{\sqrt{x}+5}+\dfrac{\sqrt{x}}{\sqrt{x}-5}+\dfrac{x+9}{25-x}\)):\(\dfrac{1-\sqrt{x}}{5+\sqrt{x}}\)
(\(\dfrac{1}{x-4}-\dfrac{1}{x-4\sqrt{x}+4}\)):\(\dfrac{\sqrt{x}}{2\sqrt{x}-x}\)
\(\dfrac{\sqrt{3-\sqrt{5}}\left(3+\sqrt{5}\right)}{\sqrt{10}+\sqrt{2}}\)
\(\dfrac{10+2\sqrt{10}}{\sqrt{5}+\sqrt{2}}\)+\(\dfrac{8}{1-\sqrt{5}}\)
\(\dfrac{5+\sqrt{7}}{9-\sqrt{23+8\sqrt{7}}}\)+\(\dfrac{5-\sqrt{7}}{2+\sqrt{16+6\sqrt{7}}}\)
\(\dfrac{1}{\sqrt{2}+\sqrt{2+\sqrt{3}}}\)+\(\dfrac{1}{\sqrt{2}-\sqrt{2+\sqrt{3}}}\)
tính
g. \(\dfrac{\sqrt{15}-\sqrt{5}}{\sqrt{3}-1}\)-\(\dfrac{9-4\sqrt{5}}{2\sqrt{5}-4}\)
h.\(\dfrac{2\sqrt{8}-\sqrt{12}}{\sqrt{18}-\sqrt{48}}\)-\(\dfrac{\sqrt{5}+\sqrt{27}}{\sqrt{30}+\sqrt{162}}\)
giải các phương trình sau:
\(1,\sqrt{18x}-6\sqrt{\dfrac{2x}{9}}=3-\sqrt{\dfrac{x}{2}}\)
\(2,\sqrt{3x}-2\sqrt{12x}+\dfrac{1}{3}\sqrt{27x}=-4\)
3, \(3\sqrt{2x}+5\sqrt{8x}-20-\sqrt{18}=0\)
\(4,\sqrt{16x+16}-\sqrt{9x+9}=1\)
\(5,\sqrt{4\left(1-3x\right)}+\sqrt{9\left(1-3x\right)}=10\)
\(6,\dfrac{2}{3}\sqrt{x-3}+\dfrac{1}{6}\sqrt{x-3}-\sqrt{x-3}=\dfrac{-2}{3}\)
