Mọi người giúp em với
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(-23,8\cdot41,9-23,8\cdot67,2+23,8\cdot9,1\)
\(=-23,8\cdot\left(41,9+67,2-9,1\right)\)
\(=-23,8\cdot100\)
\(=-2380\)
![](https://rs.olm.vn/images/avt/0.png?1311)
1/B. opportunity
2/B. go out of
3/C. focuses on science and engineering
4/B. It is the oldest university in the world.
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(A=\dfrac{x+\sqrt{xy}}{y+\sqrt{xy}}=\dfrac{\sqrt{x}\left(\sqrt{x}+\sqrt{y}\right)}{\sqrt{y}\left(\sqrt{x}+\sqrt{y}\right)}=\dfrac{\sqrt{x}}{\sqrt{y}}\)
b) \(B=\dfrac{\sqrt{a}+a\sqrt{b}-\sqrt{b}-b\sqrt{a}}{ab-1}=\dfrac{\sqrt{a}\left(1+\sqrt{ab}\right)-\sqrt{b}\left(1+\sqrt{ab}\right)}{\left(\sqrt{ab}-1\right)\left(1+\sqrt{ab}\right)}=\dfrac{\left(1+\sqrt{ab}\right)\left(\sqrt{a}-\sqrt{b}\right)}{\sqrt{ab}-1}=\dfrac{\sqrt{a}-\sqrt{b}}{\sqrt{ab}-1}\)
c) \(C=\dfrac{1+x\sqrt{x}}{1+\sqrt{x}}=\dfrac{\left(1+\sqrt{x}\right)\left(1-\sqrt{x}+x\right)}{1+\sqrt{x}}=1-\sqrt{x}+x\)
d) \(D=\dfrac{x\sqrt{x}+y\sqrt{y}}{\sqrt{x}+\sqrt{y}}-\left(\sqrt{x}-\sqrt{y}\right)^2=\dfrac{\left(\sqrt{x}+\sqrt{y}\right)\left(x-\sqrt{xy}+y\right)}{\sqrt{x}+\sqrt{y}}-x+2\sqrt{xy}-y=x-\sqrt{xy}+y-x+2\sqrt{xy}-y=\sqrt{xy}\)
e) \(\dfrac{x+4\sqrt{x}+4}{\sqrt{x}+2}+\dfrac{4-x}{2-\sqrt{x}}=\dfrac{\left(\sqrt{x}+2\right)^2}{\sqrt{x}+2}+\dfrac{\left(2-\sqrt{x}\right)\left(2+\sqrt{x}\right)}{2-\sqrt{x}}=\sqrt{x}+2+2+\sqrt{x}=2\sqrt{x}+4\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\((1) C_6H_5C_2H_5 + Cl_2 \xrightarrow{t^o,Fe} C_6H_4ClC_2H_5 + HCl\\ (2) C_6H_5C_2H_5 + Cl_2 \xrightarrow{ánh\ sáng} C_6H_5CHCl-CH_3 + HCl\)