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25 tháng 6 2018
Bài này không sai đề , tớ làm lại cho :
\(\sqrt{13-\sqrt{160}}-\sqrt{53+4\sqrt{90}}=\sqrt{13-4\sqrt{10}}-\sqrt{53+12\sqrt{10}}=\sqrt{8-2.2\sqrt{2}.\sqrt{5}+5}-\sqrt{45+2.3\sqrt{5}.2\sqrt{2}+8}=\sqrt{\left(2\sqrt{2}-\sqrt{5}\right)^2}-\sqrt{\left(3\sqrt{5}+2\sqrt{2}\right)^2}=\text{ |}2\sqrt{2}-\sqrt{5}\text{ |}-\text{ |}3\sqrt{5}+2\sqrt{2}\text{ |}=4\sqrt{2}-4\sqrt{5}\)
HH
25 tháng 6 2018
Đề này mình làm không ra nên mình sẽ sửa đề.
Giải:
\(\sqrt{14-\sqrt{160}}-\sqrt{49+4\sqrt{90}}\)
\(=\sqrt{14-4\sqrt{10}}-\sqrt{49+12\sqrt{10}}\)
\(=\sqrt{10-4\sqrt{10}+4}-\sqrt{40+12\sqrt{10}+9}\)
\(=\sqrt{\left(\sqrt{10}\right)^2-2.\sqrt{10}.2+2^2}-\sqrt{\left(2\sqrt{10}\right)^2+2.2\sqrt{10}.3+3^2}\)
\(=\sqrt{\left(\sqrt{10}-2\right)^2}-\sqrt{\left(2\sqrt{10}+3\right)^2}\)
\(=\sqrt{10}-2-\left(2\sqrt{10}+3\right)\)
\(=\sqrt{10}-2-2\sqrt{10}-3\)
\(=-\sqrt{10}-5\)
Vậy ...
Nếu sai mong bạn thông cảm
NN
1
26 tháng 6 2018
\(\sqrt{13-\sqrt{160}}-\sqrt{53+4\sqrt{90}}\)
\(=\sqrt{8-2.2\sqrt{2}.\sqrt{5}+5}-\sqrt{45+2.3\sqrt{5}.2\sqrt{2}+8}\)
\(=\sqrt{\left(2\sqrt{2}-\sqrt{5}\right)^2}-\sqrt{\left(3\sqrt{5}+2\sqrt{2}\right)^2}\)
\(=|2\sqrt{2}-\sqrt{5}|-|3\sqrt{5}+2\sqrt{2}|\)
\(=2\sqrt{2}-\sqrt{5}-3\sqrt{5}-2\sqrt{2}\)
\(=-4\sqrt{5}\)
HN
1
ND
2
28 tháng 6 2017
\(\sqrt{13-\sqrt{160}}-\sqrt{53+4\sqrt{90}}\)= -8,94427191 NHOA!
Nguyễn Diễm Quỳnh
K VÀ KB NHOA !
28 tháng 6 2017
\(B=\sqrt{13-\sqrt{160}}-\sqrt{53+4\sqrt{90}}\)
\(\Leftrightarrow B=\sqrt{13-4\sqrt{10}}-\sqrt{53+12\sqrt{10}}\)
\(\Leftrightarrow B^2=66+8\sqrt{10}-2.\sqrt{13-4\sqrt{10}}.\sqrt{53+12\sqrt{10}}\)
\(=66+8\sqrt{10}-2.\sqrt{209-56\sqrt{10}}\)
\(=66+8\sqrt{10}-2.\sqrt{\left(4\sqrt{10}-7\right)^2}\)
\(=66+8\sqrt{10}-8\sqrt{10}+14=80\)
\(\Rightarrow B=-\sqrt{80}=-4\sqrt{5}\)
NT
0
CH
2
21 tháng 6 2015
\(\sqrt{13-4\sqrt{10}}-\sqrt{53+4\sqrt{90}}\)
\(=\sqrt{\left(2\sqrt{2}\right)^2-2.2\sqrt{2}\sqrt{5}+\left(\sqrt{5}\right)^2}-\sqrt{\left(2\sqrt{2}\right)^2+2.2\sqrt{2}.3.\sqrt{5}+\left(3\sqrt{5}\right)^2}\)
\(=\sqrt{\left(2\sqrt{2}-\sqrt{5}\right)^2}-\sqrt{\left(2\sqrt{2}+3\sqrt{5}\right)^2}\)
= \(\) \(2\sqrt{2}-\sqrt{5}-2\sqrt{2}-3\sqrt{5}=-4\sqrt{5}\)
FM
1
27 tháng 9 2015
\(\sqrt{13-\sqrt{160}}-\sqrt{53+4\sqrt{90}}=\sqrt{\left(2\sqrt{2}\right)^2-2.\left(2\sqrt{2}\right).\sqrt{5}+\left(\sqrt{5}\right)^2}-\sqrt{\left(2\sqrt{2}\right)^2+2.2\sqrt{2}.\sqrt{45}+\left(\sqrt{45}\right)^2}\)
\(=2\sqrt{2}-\sqrt{5}-2\sqrt{2}-3\sqrt{5}=-4\sqrt{5}\)
NA
1
MT
2 tháng 7 2016
\(D=\sqrt{13-\sqrt{160}}-\sqrt{53+4\sqrt{90}}=\sqrt{13-4\sqrt{10}}-\sqrt{53+12\sqrt{10}}\)
\(=\sqrt{8-2.2\sqrt{2}\sqrt{5}+5}-\sqrt{\text{coi lại đề}}\)
PA
3 tháng 8 2017
\(\left(2\sqrt{4+\sqrt{6-2\sqrt{5}}}\right)\left(\sqrt{10}-\sqrt{2}\right)\)
\(=2\sqrt{4+\sqrt{\left(\sqrt{5}-1\right)^2}}\times\sqrt{2}\left(\sqrt{5}-1\right)\)
\(=2\sqrt{3+\sqrt{5}}\times\sqrt{2}\left(\sqrt{5}-\sqrt{1}\right)\)
\(=2\sqrt{6+2\sqrt{5}}\times\left(\sqrt{5}-\sqrt{1}\right)\)
\(=2\sqrt{\left(\sqrt{5}+1\right)^2}\times\left(\sqrt{5}-\sqrt{1}\right)\)
\(=2\left(\sqrt{5}+1\right)\times\left(\sqrt{5}-\sqrt{1}\right)\)
\(=2\left(5-1\right)\)
= 8
~ ~ ~
\(\sqrt{13-\sqrt{160}}-\sqrt{53+4\sqrt{90}}\)
\(=\sqrt{13-4\sqrt{10}}-\sqrt{53+12\sqrt{10}}\)
\(=\sqrt{\left(2\sqrt{2}-\sqrt{5}\right)^2}-\sqrt{\left(3\sqrt{5}+2\sqrt{2}\right)^2}\)
\(=\left(2\sqrt{2}-\sqrt{5}\right)-\left(3\sqrt{5}+2\sqrt{2}\right)\)
\(=-4\sqrt{5}\)
3 tháng 8 2017
a. \(\left(2\sqrt{4+\sqrt{6-2\sqrt{5}}}\right)\left(\sqrt{10}-\sqrt{2}\right)=\left[2\sqrt{4+\sqrt{\left(\sqrt{5}-1\right)^2}}\right]\left(\sqrt{10}-\sqrt{2}\right)=\left(2\sqrt{4+\sqrt{5}-1}\right)\left(\sqrt{10}-\sqrt{2}\right)=\left(2\sqrt{3+\sqrt{5}}\right)\left(\sqrt{10}-\sqrt{2}\right)=\left[2\sqrt{\left(\sqrt{\dfrac{5}{2}}+\sqrt{\dfrac{1}{2}}\right)^2}\right]\left(\sqrt{10}-\sqrt{2}\right)=\left[2\left(\sqrt{\dfrac{5}{2}}+\sqrt{\dfrac{1}{2}}\right)\right]\left(\sqrt{10}-\sqrt{2}\right)=\left(\sqrt{10}+\sqrt{2}\right)\left(\sqrt{10}-\sqrt{2}\right)=10-2=8\)
b. \(\sqrt{13-\sqrt{160}}-\sqrt{53+4\sqrt{90}}=\sqrt{\left(2\sqrt{2}-\sqrt{5}\right)^2}-\sqrt{\left(3\sqrt{5}+2\sqrt{2}\right)^2}=2\sqrt{2}-\sqrt{5}-3\sqrt{5}-2\sqrt{2}=-4\sqrt{5}\)
8 tháng 7 2018
a) \(\sqrt{13-\sqrt{160}}-\sqrt{53+4\sqrt{90}}\)
\(=\sqrt{13-2\sqrt{40}}-\sqrt{53+12\sqrt{10}}\)
\(=\sqrt{\left(\sqrt{8}\right)^2-2.\sqrt{8}.\sqrt{5}+\left(\sqrt{5}\right)^2}-\sqrt{\left(3\sqrt{5}\right)^2+2.3\sqrt{5}.2\sqrt{2}+\left(2\sqrt{2}\right)^2}\)
\(=\sqrt{\left(\sqrt{8}-\sqrt{5}\right)^2}-\sqrt{\left(3\sqrt{5}+2\sqrt{2}\right)^2}\)
\(=\left|\sqrt{8}-\sqrt{5}\right|-\left|3\sqrt{5}+2\sqrt{2}\right|\)
= √8 - √5 - 3√5 - 2√2 = -4√5
b) (1+√3-√2).(1+√3+√2)= [(1+√3)^2-(√2)^2] = 4+2√3-2=2+2√3
8 tháng 7 2018
a) =sprt{13-=sprt{160}} - =sprt{53+4=sprt{90}}
= =sprt{(=sprt{8} - =sprt{5})2 } - =sprt{(=sprt{45} + =sprt{8})2 }
= =sprt{8} - =sprt{5} - =sprt{45} - =sprt{8}
= -3=sprt{5}
b) ( 1 + =sprt{3} - =sprt{2} )( 1+ =sprt{3} + =sprt{2} )
= ( 1 + =sprt{3} )2 - (=sprt{2})2
= 4 + 2=sprt{3} - 2
=2 + 2=sprt{3}
\(\sqrt{13-\sqrt{160}}+\sqrt{53+4\sqrt{90}}\)
\(=\sqrt{13-4\sqrt{10}}+\sqrt{53+12\sqrt{10}}\)
\(=2\sqrt{2}-\sqrt{5}+3\sqrt{5}-2\sqrt{2}\)
\(=2\sqrt{5}\)
`\sqrt{13-\sqrt{160}}+\sqrt{53+4\sqrt{90}}`
`=\sqrt{8-2.2\sqrt{2}.\sqrt{5}+5}+\sqrt{45+2.3\sqrt{5}.2\sqrt{2}+8}`
`=\sqrt{(2\sqrt{2}-\sqrt{5})^2}+\sqrt{(3\sqrt{5}+2\sqrt{2})^2}`
`=|2\sqrt{2}-\sqrt{5}|+3\sqrt{5}+2\sqrt{2}`
`=2\sqrt{2}-\sqrt{5}+3\sqrt{5}+2\sqrt{2}`
`=4\sqrt{2}+2\sqrt{5}`