thời gian đi là ;

10h -2h =8 h

Sab=8*30+40*8=560 km

1E

2H

3F

4C

5B

6D

a, \(2\sqrt{3}-\sqrt{4+x^2}=0\Leftrightarrow\sqrt{4+x^2}=2\sqrt{3}\)

\(\Leftrightarrow x^2+4=12\Leftrightarrow x^2=8\Leftrightarrow x=\pm2\sqrt{2}\)

b, \(\sqrt{16x+16}-\sqrt{9x+9}=0\)ĐK : x >= -1 

\(\Leftrightarrow4\sqrt{x+1}-3\sqrt{x+1}=0\Leftrightarrow\sqrt{x+1}=0\Leftrightarrow x+1=0\Leftrightarrow x=-1\)

c, \(\sqrt{4\left(x+2\right)^2}=8\Leftrightarrow2\left|x+2\right|=8\Leftrightarrow\left|x+2\right|=4\)

TH1 : \(x+2=4\Leftrightarrow x=2\)

TH2 : \(x+2=-4\Leftrightarrow x=-6\)

c: Ta có: \(\sqrt{4\left(x+2\right)^2}=8\)

\(\Leftrightarrow\left|x+2\right|=4\)

\(\Leftrightarrow\left[{}\begin{matrix}x+2=4\\x+2=-4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-6\end{matrix}\right.\)

\(3\sqrt{x}-2x=0\)

\(\Leftrightarrow3\sqrt{x}=2x\)

\(\Leftrightarrow\sqrt{x}=\frac{2x}{3}\)

\(\Leftrightarrow\left(\sqrt{x}\right)^2=\frac{4x^2}{9}\)

\(\Leftrightarrow x=\frac{4x^2}{9}\)

\(\Leftrightarrow\frac{4x^2}{x}=9\)

\(\Leftrightarrow4x=9\)

\(\Leftrightarrow x=\frac{9}{4}\)

\(3\sqrt{x}-2x=0\)

\(\Leftrightarrow9x-4x^2=0\)

\(\Leftrightarrow x\left(9-4x\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x=0\\9-4x=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=0\\x=\frac{9}{4}\end{cases}}}\)

a) \(\sqrt{\left(\sqrt{2}-1\right)^2}-\sqrt{11+6\sqrt{2}}\)

\(=\sqrt{2}-1-3-\sqrt{2}\)

=-4

b) \(\sqrt{\left(1-\sqrt{5}\right)^2}+\sqrt{14-6\sqrt{5}}\)

\(=\sqrt{5}-1+3-\sqrt{5}\)

=2

c) \(\sqrt{21-12\sqrt{3}}-\sqrt{13-4\sqrt{3}}\)

\(=2\sqrt{3}-3-2\sqrt{3}+1\)

=-2

bạn tự làm đi