Câu 1:
1:
a) Ta có: \(A=3\sqrt{49}-\sqrt{25}\)
\(=3\cdot7-5\)
\(=21-5=16\)
Câu 1:
1:
b) Ta có: \(B=\sqrt{\left(3-2\sqrt{5}\right)^2}-\sqrt{20}\)
\(=2\sqrt{5}-3-2\sqrt{5}\)
=-3
Câu 1:
2:
a) Ta có: \(P=\left(\dfrac{\sqrt{x}}{\sqrt{x}-1}+\dfrac{\sqrt{x}}{x-\sqrt{x}}\right):\dfrac{\sqrt{x}+1}{3}\)
\(=\dfrac{\sqrt{x}+1}{\sqrt{x}-1}\cdot\dfrac{3}{\sqrt{x}+1}\)
\(=\dfrac{3}{\sqrt{x}-1}\)
Câu 1:
2:
b) Để P=1 thì \(\dfrac{3}{\sqrt{x}-1}=1\)
\(\Leftrightarrow\sqrt{x}-1=3\)
\(\Leftrightarrow\sqrt{x}=4\)
hay x=16(thỏa ĐK)
Vậy: Để P=1 thì x=16
Câu 2:
1: Ta có: \(\left\{{}\begin{matrix}3x+2y=7\\2x+y=4\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}6x+4y=14\\6x+3y=12\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=2\\2x=4-y=2\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=1\\y=2\end{matrix}\right.\)
Vậy: (x,y)=(1;2)
