giúp mik với
a) \(\left(4\sqrt{x}-7\right)\left(4\sqrt{x}+7\right)=0\left(đk:x\ge0\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}4\sqrt{x}-7=0\\4\sqrt{x}+7=0\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x}=\dfrac{7}{4}\left(tm\right)\\\sqrt{x}=-\dfrac{7}{4}\left(VLý\right)\end{matrix}\right.\)
\(\Leftrightarrow x=\dfrac{49}{16}\left(tm\right)\)
b) \(\Leftrightarrow\left(x-\sqrt{13}\right)^2=0\)
\(\Leftrightarrow x=\sqrt{13}\)
Bài 5:
\(\sqrt{4+2\sqrt{3}}-\sqrt{4-2\sqrt{3}}\)
\(=\sqrt{\left(\sqrt{3}+1\right)^2}-\sqrt{\left(\sqrt{3}-1\right)^2}\)
\(=\left|\sqrt{3}+1\right|-\left|\sqrt{3}-1\right|\)
\(=\sqrt{3}+1-\sqrt{3}+1=2\left(đpcm\right)\)
