a.
Biểu thức có nghĩa khi: \(5-2x\ge0\Leftrightarrow x\le\dfrac{5}{2}\)
b.
\(\dfrac{1}{3}\sqrt{153}=\sqrt{\dfrac{153}{9}}=\sqrt{17}\)
\(3\sqrt{2}=\sqrt{3^2.2}=\sqrt{18}\)
Mà \(\sqrt{18}>\sqrt{17}\Rightarrow3\sqrt{2}>\dfrac{1}{3}\sqrt{153}\)
c.
\(=\left(\dfrac{\left(1-\sqrt{b}\right)\left(1+\sqrt{b}+b\right)}{1-\sqrt{b}}+\sqrt{b}\right)\left(\dfrac{1-\sqrt{b}}{\left(1-\sqrt{b}\right)\left(1+\sqrt{b}\right)}\right)^2\)
\(=\left(b+2\sqrt{b}+1\right)\left(\dfrac{1}{\left(1+\sqrt{b}\right)}\right)^2=\left(1+\sqrt{b}\right)^2.\dfrac{1}{\left(1+\sqrt{b}\right)^2}\)
\(=1\) (đpcm)
a) ĐKXĐ: \(x\le\dfrac{5}{2}\)
b) \(\dfrac{1}{3}\sqrt{153}=\dfrac{1}{3}\cdot3\sqrt{17}=\sqrt{17}\)
\(3\sqrt{2}=\sqrt{18}\)
Do đó: \(\dfrac{1}{3}\sqrt{153}< 3\sqrt{2}\)
