Tính \(\sqrt{16};\sqrt{25};\sqrt{165};\sqrt{1};\sqrt{0};\sqrt{3}\)
tính A=\(\sqrt{24+16\sqrt{2}}-\sqrt{24-16\sqrt{2}}\)
\(A=\sqrt{24+16\sqrt{2}}-\sqrt{24-16\sqrt{2}}=\sqrt{\left(4+\sqrt{8}\right)^2}-\sqrt{\left(4-\sqrt{8}\right)^2}=\left|4+\sqrt{8}\right|-\left|4-\sqrt{8}\right|=4+\sqrt{8}-4+\sqrt{8}=4\sqrt{2}\)
\(A=\sqrt{24+16\sqrt{2}}-\sqrt{24-16\sqrt{2}}\)
\(=\sqrt{8+2.4.2\sqrt{2}+16}-\sqrt{16-2.4.2\sqrt{2}+8}\)
\(=\sqrt{\left(2\sqrt{2}+4\right)^2}-\sqrt{\left(4-2\sqrt{2}\right)^2}\)
\(=2\sqrt{2}+4-4+2\sqrt{2}\)
\(=4\sqrt{2}\)
tính x=\(\sqrt{97-56\sqrt{3}}+\sqrt{52+16\sqrt{3}}\)
y=\(\sqrt{33+20\sqrt{2}}+\sqrt{24-16\sqrt{2}}\)
Ta có: \(x=\sqrt{97-56\sqrt{3}}+\sqrt{52+16\sqrt{3}}\)
\(=\sqrt{49-2\cdot7\cdot4\sqrt{3}+48}+\sqrt{48+2\cdot4\sqrt{3}\cdot2+4}\)
\(=\sqrt{\left(7-4\sqrt{3}\right)^2}+\sqrt{\left(4\sqrt{3}+2\right)^2}\)
\(=\left|7-4\sqrt{3}\right|+\left|4\sqrt{3}+2\right|\)
\(=7-4\sqrt{3}+4\sqrt{3}+2\)
\(=9\)
Làm luôn phần y :D
y = \(\sqrt{33+20\sqrt{2}}+\sqrt{24-16\sqrt{2}}\)
y = \(\sqrt{33+2.10\sqrt{2}}+\sqrt{24-2.8\sqrt{2}}\)
y = \(\sqrt{33+2.5.2\sqrt{2}}+\sqrt{24-2.4.2\sqrt{2}}\)
y = \(\sqrt{25+2.5.\sqrt{8}+8}+\sqrt{16-2.4.\sqrt{8}+8}\)
y = \(\sqrt{\left(5+\sqrt{8}\right)^2}+\sqrt{\left(4-\sqrt{8}\right)^2}\)
y = |5 + \(\sqrt{8}\)| + |4 - \(\sqrt{8}\)|
y = 5 + \(\sqrt{8}\) + 4 - \(\sqrt{8}\) (Vì 4 > \(\sqrt{8}\) nên 4 - \(\sqrt{8}\) > 0)
y = 9
Vậy y = 9
Chúc bn học tốt!
Tính B=\(x^3-3x+1077\)
với x=\(\sqrt[3]{16-\sqrt{255}}+\dfrac{1}{\sqrt[3]{16-\sqrt{255}}}\)
\(x^3=\left(\sqrt[3]{16-\sqrt{255}}+\dfrac{1}{\sqrt[3]{16-\sqrt{255}}}\right)^3\)
=>\(x^3=16-\sqrt{255}+\dfrac{1}{16-\sqrt{255}}+3\cdot x\cdot\sqrt[3]{\left(16-\sqrt{255}\right)\cdot\dfrac{1}{16-\sqrt{255}}}\)
=>\(x^3=16-\sqrt{255}+\dfrac{1}{16-\sqrt{255}}+3x\)
=>\(x^3-3x=16-\sqrt{255}+\dfrac{1}{16-\sqrt{255}}\)
=>\(B=16-\sqrt{255}+\dfrac{1}{16-\sqrt{255}}+1077\)
\(=1093-\sqrt{255}+\dfrac{16+\sqrt{255}}{1}\)
\(=1093-\sqrt{255}+16+\sqrt{255}\)
=1093+16
=1109
Tính:
\(\left(\frac{2}{5}.\sqrt{16}+2\sqrt{\frac{16}{25}}\right):2\sqrt{\frac{1}{16}}\)
\(\left(\frac{2}{5}\sqrt{16}+2\sqrt{\frac{16}{25}}\right):2\sqrt{\frac{1}{16}}=\left(\frac{2}{5}.\sqrt{4^2}+2\sqrt{\frac{4^2}{5^2}}\right):\frac{2}{\sqrt{4^2}}\)
\(=\left(\frac{2}{5}.4+2.\frac{4}{5}\right).2=\left(\frac{8}{5}+\frac{8}{5}\right).2=\frac{32}{5}\)
\(\left(\frac{2}{5}.\sqrt{16}+2\sqrt{\frac{16}{25}}\right):2\sqrt{\frac{1}{16}}\)
\(=\left(\frac{2}{5}.4+2.\frac{4}{5}\right):2.\frac{1}{4}\)
\(=\left(\frac{8}{5}+\frac{8}{5}\right):\frac{1}{2}\)
\(=\frac{16}{5}:\frac{1}{2}\)
\(=\frac{32}{5}\)
^...^ ^_^
\(\left(\frac{2}{5}\sqrt{16}+2\sqrt{\frac{16}{25}}\right):2\sqrt{\frac{1}{16}}\)
\(=\left(\frac{2}{5}.4+2.\frac{4}{5}\right):2.\frac{1}{4}\)
\(=\left(\frac{8}{5}+\frac{8}{5}\right):\frac{1}{2}\)
\(=\frac{16}{5}:\frac{1}{2}\)
\(=\frac{16}{5}.2\)
\(=\frac{32}{5}\)
Tính \(a=\sqrt[3]{16-8\sqrt{5}}+\sqrt[3]{16+8\sqrt{5}}\)
\(\sqrt[3]{16-8\sqrt{5}}\)=\(\sqrt[3]{1-3\sqrt{5}+15-5\sqrt{5}}\)=\(\sqrt[3]{1-3\sqrt{5}+3\left(\sqrt{5}\right)^2-\left(\sqrt{5}\right)^3}\)=\(\sqrt[3]{\left(1-\sqrt{5}\right)^3}\)=\(1-\sqrt{5}\)
làm tương tự: \(\sqrt[3]{16+8\sqrt{5}}\)=\(1+\sqrt{5}\)
suy ra: a = 2
thực hiện phép tính
\(\left(\dfrac{15}{\sqrt{6}+1}+\dfrac{4}{\sqrt{16}-2}-\dfrac{12}{3-\sqrt{16}}\right).\left(\sqrt{6}+11\right)\)
Lời giải:
\(\left(\frac{15}{\sqrt{6}+1}+\frac{4}{\sqrt{16}-2}-\frac{12}{3-\sqrt{16}}\right).(\sqrt{6}+11)=\left(\frac{15(\sqrt{6}-1)}{(\sqrt{6}+1)(\sqrt{6}-1)}+\frac{4}{4-2}-\frac{12}{3-4}\right)(\sqrt{6}+11)\)
\(=\left(\frac{15(\sqrt{6}-1)}{6-1}+2+12\right)(\sqrt{6}+11)=(3\sqrt{6}-3+14)(\sqrt{6}+11)\)
\(=(3\sqrt{6}+11)(\sqrt{6}+11)\)
Tính: \(\dfrac{\sqrt{26}}{\sqrt[2]{17576}}.\dfrac{\sqrt{6}.\sqrt{16}}{\sqrt{2}}\)
\(=\dfrac{\sqrt{26}}{\sqrt{676.26}}.\dfrac{\sqrt{6}.4}{\sqrt{2}}=\dfrac{\sqrt{26}}{\sqrt{676}.\sqrt{26}}.\dfrac{\sqrt{12}.4}{2}=\dfrac{4\sqrt{3}}{26}=\dfrac{2\sqrt{3}}{13}\)
Tính: \(a)\sqrt {16} ;b)\sqrt {81} ;c)\sqrt {{{2021}^2}} \)
a) Vì \({4^2} = 16\) nên \(\sqrt {16} = 4\)
b) Vì \({9^2} = 81\) nên \(\sqrt {81} = 9\)
c) Vì 2021 > 0 nên \(\sqrt {{{2021}^2}} = 2021\)
Không sử dụng máy tính cầm tay, hãy so sánh các số sau:
a) \(\sqrt {42} \) và \(\sqrt[3]{{51}}\)
b) \({16^{\sqrt 3 }}\) và \({4^{3\sqrt 2 }}\)
c) \({(0,2)^{\sqrt {16} }}\) và \({\left( {0,2} \right)^{\sqrt[3]{{60}}}}\)
\(a,\sqrt{42}=\sqrt{3\cdot14}>\sqrt{3\cdot12}=6\\ \sqrt[3]{51}=\sqrt[3]{17}< \sqrt[3]{3\cdot72}=6\\ \Rightarrow\sqrt{42}>\sqrt[3]{51}\\ b,16^{\sqrt{3}}=4^{2\sqrt{3}}\\ 18>12\Rightarrow3\sqrt{2}>2\sqrt{3}\Rightarrow4^{3\sqrt{2}}>4^{2\sqrt{3}}\\ \Rightarrow4^{3\sqrt{2}}>16^{\sqrt{3}}\)
\(c,\left(\sqrt{16}\right)^6=16^3=4^6=4^2\cdot4^4=4^2\cdot16^2\\ \left(\sqrt[3]{60}\right)^6=60^2=4^2\cdot15^2\\ 4^2\cdot16^2>4^2\cdot15^2\Rightarrow\sqrt{16}>\sqrt[3]{60}\Rightarrow0,2^{\sqrt{16}}< 0,2^{\sqrt[3]{60}}\)
tính \(\left(3\sqrt{2}\right)^2\sqrt{\dfrac{2}{16-6\sqrt{7}}}\)
`(3\sqrt2)^2.\sqrt(2/(16-6\sqrt7))`
`=18. \sqrt(2/(9-6\sqrt7+7))`
`=18 .\sqrt(2/(3^2-2.3.\sqrt7+\sqrt7^2))`
`=18 .\sqrt(2/((3-\sqrt7)^2))`
`= 18. \sqrt2/(3-\sqrt7)`
`=18 . (\sqrt14+3\sqrt2)/2`
`=9+\sqrt14+27\sqrt2`
\(\left(3\sqrt{2}\right)^2\cdot\sqrt{\dfrac{2}{16-6\sqrt{7}}}\)
\(=18\cdot\dfrac{\sqrt{2}}{3-\sqrt{7}}\)
\(=\dfrac{18\sqrt{2}}{3-\sqrt{7}}=9\sqrt{14}+27\sqrt{2}\)