Chứng minh đẳng thức.
\(\sqrt{9-4\sqrt{5}}-\sqrt{5}=-2\)
Những câu hỏi liên quan
Chứng minh đẳng thức sau:
\(\frac{a+\sqrt{2+\sqrt{5}}.\sqrt{\sqrt{9-4\sqrt{5}}}}{\sqrt[3]{2-\sqrt{5}}.\sqrt[3]{\sqrt{9+4\sqrt{5}}-\sqrt[3]{a^2}}+\sqrt[3]{a}}=-\sqrt[3]{a-1}\)
Chứng minh bất đẳng thức sau:
\(\left(\sqrt[3]{\sqrt{9+4\sqrt{5}}+\sqrt[3]{2+\sqrt{5}}}\right).\sqrt[3]{\sqrt{5-2}}-2,1< 0\)
Chứng minh đẳng thức
\(\sqrt{9-4\sqrt{5}}-\sqrt{5}=-2\)
CM : \(\sqrt{9-4\sqrt{5}}-\sqrt{5}=-2\)
Giải :
VT= \(\sqrt{9-4\sqrt{5}}-\sqrt{5}=\sqrt{\left(\sqrt{5}-2\right)^2}-\sqrt{5}=\left|\sqrt{5}-2\right|-\sqrt{5}=\sqrt{5}-2-\sqrt{5}=-2\)
Thấy VT = VP = - 2
=> \(\sqrt{9-4\sqrt{5}}-\sqrt{5}=-2\) ( đpcm )
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Chứng minh đẳng thức:
\(\sqrt{9-4\sqrt{5}}-\sqrt{5}=-2\)
\(\sqrt{23+8\sqrt{7}}-\sqrt{7=4}\)
\(\sqrt{\sqrt{5}^2-2.2\sqrt{5}+4}-\sqrt{5}=\sqrt{\left(\sqrt{5}-2\right)^2}-\sqrt{5}=\sqrt{5}-2-\sqrt{5}=-2\left(dpcm\right)\)\(\sqrt{23+8\sqrt{7}}-\sqrt{7}=\sqrt{\sqrt{7}^2+2.4\sqrt{7}+16}-\sqrt{7}\)\(=\sqrt{\left(\sqrt{7}+4\right)^2}-\sqrt{7}=\sqrt{7}+4-\sqrt{7}=4\left(DPCM\right)\)
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Chứng minh đẳng thức
\(\left(4-\sqrt{7}\right)^2=23-8\sqrt{7}\)
\(\sqrt{9-4\sqrt{5}}-\sqrt{5}=-2\)
\(\dfrac{\sqrt{4-2\sqrt{3}}}{1+\sqrt{2}}:\dfrac{\sqrt{2}-1}{\sqrt{3}+1}=2\)
\(\left(\dfrac{2\sqrt{3}-\sqrt{6}}{\sqrt{8}-2}-\dfrac{\sqrt{216}}{3}\right).\dfrac{1}{\sqrt{6}}=-1,5\)
\(\left(4-\sqrt{7}\right)^2=4^2-2\cdot4\cdot\sqrt{7}+7\)
\(=16-8\sqrt{7}+7=23-8\sqrt{7}\)
\(\sqrt{9-4\sqrt{5}}-\sqrt{5}\)
\(=\sqrt{5-2\cdot\sqrt{5}\cdot2+4}-\sqrt{5}\)
\(=\sqrt{\left(\sqrt{5}-2\right)^2}-\sqrt{5}\)
\(=\left|\sqrt{5}-2\right|-\sqrt{5}\)
\(=\sqrt{5}-2-\sqrt{5}=-2\)
\(\dfrac{\sqrt{4-2\sqrt{3}}}{1+\sqrt{2}}:\dfrac{\sqrt{2}-1}{\sqrt{3}+1}\)
\(=\dfrac{\sqrt{3-2\cdot\sqrt{3}\cdot1+1}}{\sqrt{2}+1}\cdot\dfrac{\sqrt{3}+1}{\sqrt{2}-1}\)
\(=\dfrac{\sqrt{\left(\sqrt{3}-1\right)^2}}{\sqrt{2}+1}\cdot\dfrac{\sqrt{3}+1}{\sqrt{2}-1}\)
\(=\dfrac{\left(\sqrt{3}-1\right)\left(\sqrt{3}+1\right)}{\left(\sqrt{2}+1\right)\left(\sqrt{2}-1\right)}=\dfrac{3-1}{2-1}=2\)
\(\left(\dfrac{2\sqrt{3}-\sqrt{6}}{\sqrt{8}-2}-\dfrac{\sqrt{216}}{3}\right)\cdot\dfrac{1}{\sqrt{6}}\)
\(=\left(\dfrac{\sqrt{6}\left(\sqrt{2}-1\right)}{2\left(\sqrt{2}-1\right)}-\dfrac{6\sqrt{6}}{3}\right)\cdot\dfrac{1}{\sqrt{6}}\)
\(=\left(\dfrac{1}{2}\sqrt{6}-2\sqrt{6}\right)\cdot\dfrac{1}{\sqrt{6}}\)
\(=\dfrac{1}{2}-2=-\dfrac{3}{2}=-1,5\)
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Chứng minh đẳng thức
\(\left(4-\sqrt{7}\right)^2=23-8\sqrt{7}\)
\(\sqrt{9-4\sqrt{5}}-\sqrt{5}=-2\)
\(\dfrac{\sqrt{4-2\sqrt{3}}}{1+\sqrt{2}}:\dfrac{\sqrt{2}-1}{\sqrt{3}-1}=2\)
\(\left(\dfrac{2\sqrt{3}-\sqrt{6}}{\sqrt{8}-2}-\dfrac{\sqrt{216}}{3}\right).\dfrac{1}{\sqrt{6}}=-1,5\)
Bài 1:Chứng minh các đẳng thức:
a) \(\sqrt{5}+\sqrt{3}=\sqrt{8+2\sqrt{3}}\)
b)\(\sqrt{5}+2=\sqrt{9+4\sqrt{5}}\)
29 tháng 6 2021 lúc 7:45
* Chứng minh đẳng thức:
\(\left(\dfrac{14}{\sqrt{14}}+\dfrac{\sqrt{12}+\sqrt{30}}{\sqrt{2}+\sqrt{5}}\right).\sqrt{5-\sqrt{21}}=4\)
\(VT=\left(\dfrac{\sqrt{14.14}}{\sqrt{14}}+\dfrac{\sqrt{6}\left(\sqrt{2}+\sqrt{5}\right)}{\sqrt{2}+\sqrt{5}}\right).\sqrt{5-\sqrt{21}}\)
\(=\left(\sqrt{14}+\sqrt{6}\right)\sqrt{5-\sqrt{21}}\)
\(=\sqrt{30-6\sqrt{21}}+\sqrt{70-14\sqrt{21}}\)
\(=\sqrt{21-2.3\sqrt{21}+9}+\sqrt{21-2.7.\sqrt{21}+49}\)
\(=\sqrt{\left(\sqrt{21}-3\right)^2}+\sqrt{\left(7-\sqrt{21}\right)^2}\)
\(=\sqrt{21}-3+7-\sqrt{21}=4\)
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7 tháng 7 2021 lúc 16:30
* Giải phương trình
\(\sqrt{4x+8}+3\sqrt{x+2}=3+\dfrac{4}{5}\sqrt{25x+50}\)
* Chứng minh đẳng thức
\(\sqrt{2+\sqrt{3}}+\sqrt{2-\sqrt{3}}=\sqrt{6}\)
\(\sqrt{4x+8}+3\sqrt{x+2}=3+\dfrac{4}{5}\sqrt{25x+50}\left(x\ge-2\right)\)
\(\Rightarrow2\sqrt{x+2}+3\sqrt{x+2}-4\sqrt{x+2}=3\Rightarrow\sqrt{x+2}=3\Rightarrow x=7\)
\(\sqrt{2+\sqrt{3}}+\sqrt{2-\sqrt{3}}=\sqrt{\dfrac{4+2\sqrt{3}}{2}}+\sqrt{\dfrac{4-2\sqrt{3}}{2}}\)
\(=\sqrt{\dfrac{\left(\sqrt{3}+1\right)^2}{2}}+\sqrt{\dfrac{\left(\sqrt{3}-1\right)^2}{2}}=\dfrac{\sqrt{3}+1}{\sqrt{2}}+\dfrac{\sqrt{3}-1}{\sqrt{2}}=\dfrac{2\sqrt{3}}{\sqrt{2}}=\sqrt{6}\)
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Chứng minh đẳng thức
\(\left(\sqrt{9-2\sqrt{14}}+\frac{5}{\sqrt{7}-\sqrt{2^{ }}}\right)^2=28\)