2. a) \(B=\left(\dfrac{\sqrt{x}+2}{x-2\sqrt{x}+1}-\dfrac{\sqrt{x}-2}{x-1}\right)\cdot\dfrac{\left(\sqrt{x}-1\right)^2}{2\sqrt{x}}\)

\(B=\left[\dfrac{\sqrt{x}+2}{\left(\sqrt{x}-1\right)^2}-\dfrac{\sqrt{x}-2}{x-1}\right]\cdot\dfrac{\left(\sqrt{x}-1\right)^2}{2\sqrt{x}}\)

\(B=\left[\dfrac{\left(\sqrt{x}+2\right)\left(x-1\right)}{\left(\sqrt{x}-1\right)^2\left(x-1\right)}-\dfrac{\left(\sqrt{x}-2\right)\left(x-2\sqrt{x}+1\right)}{\left(\sqrt{x}-1\right)^2\left(x-1\right)}\right]\cdot\dfrac{\left(\sqrt{x}-1\right)^2}{2\sqrt{x}}\)

\(B=\left[\dfrac{x\sqrt{x}-\sqrt{x}+2x-2}{\left(\sqrt{x}-1\right)^2\left(x-1\right)}-\dfrac{x\sqrt{x}-4x+5\sqrt{x}-2}{\left(\sqrt{x}-1\right)^2\left(x-1\right)}\right]\cdot\dfrac{\left(\sqrt{x}-1\right)^2}{2\sqrt{x}}\)

\(B=\dfrac{x\sqrt{x}-\sqrt{x}+2x-2-x\sqrt{x}+4x-5\sqrt{x}+2}{\left(\sqrt{x}-1\right)^2\left(x-1\right)}\cdot\dfrac{\left(\sqrt{x}-1\right)^2}{2\sqrt{x}}\)

\(B=\dfrac{6x-6\sqrt{x}}{\left(\sqrt{x}-1\right)^2\left(x-1\right)}\cdot\dfrac{\left(\sqrt{x}-1\right)^2}{2\sqrt{x}}\)

\(B=\dfrac{2\sqrt{x}\left(3\sqrt{x}-3\right)}{\left(\sqrt{x}-1\right)^2\left(x-1\right)}\cdot\dfrac{\left(\sqrt{x}-1\right)^2}{2\sqrt{x}}\)

\(B=\dfrac{3\sqrt{x}-3}{x-1}\)

\(B=\dfrac{3\left(\sqrt{x}-1\right)}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}\)

\(B=\dfrac{3}{\sqrt{x}+1}\)

b) \(B=1\Leftrightarrow\dfrac{3}{\sqrt{x}+1}=1\)

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

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

\(\Leftrightarrow x=4\)

Vận tốc:

22,5 : 2,5 = 9 (km/gio)

Thời gian để đi hết quãng đường 33,75 km: 

33,75 : 9 = 3,75 (gio)

               = 3 giờ 45 phút