Câu 4:
1: \(P=\dfrac{x-2\sqrt{x}+1-x-2\sqrt{x}-1}{\left(\sqrt{x}+1\right)\left(\sqrt{x}-1\right)}\cdot\dfrac{1-x}{\sqrt{x}}\)
\(=\dfrac{-4\sqrt{x}}{x-1}\cdot\dfrac{-\left(x-1\right)}{\sqrt{x}}=4\)
2: ĐKXĐ: \(5-2x>=0\)
=>2x<=5
hay x<=5/2
a)\(\left\{{}\begin{matrix}x-y=1\\2x+y=6065\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x-y+2x+y=6065+1\\2x+y=6065\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}3x=6066\\2x+y=6065\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=2022\\y=6065-2.2022=2021\end{matrix}\right.\)
`4x^2 -20 =0`
`<=> 4x^2 =20`
`<=> x^2 = 5`
\(\Leftrightarrow\left[{}\begin{matrix}x=\sqrt{5}\\x=-\sqrt{5}\end{matrix}\right.\)
