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Những câu hỏi liên quan
14 tháng 10 2021
5.
1. going
2.lying/reading
3.likes/ being
4.collecting
5.watching / are going
6.doing
7.plays
8.have collected
9. will travel
10.will make
6.
1.beautiful
2. boring
3. decoration
4.widens
5. wonderful
8
ST
0
ST
1
ST
1
26 tháng 9 2021
Đặt \(\dfrac{x}{4}=\dfrac{y}{7}=k\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=4k\\y=7k\end{matrix}\right.\)
Ta có: xy=112
\(\Leftrightarrow28k^2=112\)
\(\Leftrightarrow k^2=4\)
Trường hợp 1: k=2
\(\Leftrightarrow\left\{{}\begin{matrix}x=4k=4\cdot2=8\\y=7k=7\cdot2=14\end{matrix}\right.\)
Trường hợp 2: x=-2
\(\Leftrightarrow\left\{{}\begin{matrix}x=4k=-8\\y=7k=-14\end{matrix}\right.\)
17 tháng 11 2021
7. How often does he go to the library?
8. ....is the shortest student in his class.
9......is her address?
10... is shorter than Ba.
N
6 tháng 11 2021
Bài 1:
\(54\left(\dfrac{km}{h}\right)=15\left(\dfrac{m}{s}\right);9\left(\dfrac{m}{s}\right)=32,4\left(\dfrac{km}{h}\right)\)
Baì 2:
\(t'=s':v'=5:\left(5.3,6\right)=\dfrac{5}{18}h\)
\(\Rightarrow v_{tb}=\dfrac{s'+s''}{t'+t''}=\dfrac{5+3,8}{\dfrac{5}{18}+\left(\dfrac{15}{60}\right)}\simeq16,67\left(\dfrac{km}{h}\right)\)
7 tháng 11 2021
Câu 2:
\(\Leftrightarrow\left(x+2\right)\left(10x+3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=-\dfrac{3}{10}\end{matrix}\right.\)
\(1.\sqrt{10,6^2-5,6^2}=\sqrt{\left(10,6-5,6\right)\left(10,6+5,6\right)}=\sqrt{5\times16,2}=\sqrt{81}=9\)
\(2.\sqrt{20+9+2.3.2\sqrt{5}}+\sqrt{20+9-2.3.2\sqrt{5}}=\sqrt{\left(2\sqrt{5}+3\right)^2}+\sqrt{\left(2\sqrt{5}-3\right)^2}\)
\(=2\sqrt{5}+3+2\sqrt{5}-3=4\sqrt{5}\)
\(3.\frac{\sqrt{10}+\sqrt{26}}{2\sqrt{5}+\sqrt{52}}=\frac{\sqrt{2}\left(\sqrt{5}+\sqrt{13}\right)}{2\left(\sqrt{5}+\sqrt{13}\right)}=\frac{1}{\sqrt{2}}\)
\(4.\left(1-\sqrt{2}+\sqrt{3}\right)\left(1+\sqrt{2}-\sqrt{3}\right)=1-\left(\sqrt{2}-\sqrt{3}\right)^2=1-\left(5-2\sqrt{6}\right)=2\sqrt{6}-4\)
\(5.\left(\sqrt{5+\sqrt{21}}+\sqrt{5-\sqrt{21}}\right)^2=10+2\sqrt{5+\sqrt{21}}.\sqrt{5-\sqrt{21}}\)
\(=10+2\sqrt{25-21}=14\)