Toán Lớp 9: Giải ptrinh:
c) 3 √x+2 √9x = 5 √4x – 2
d) √9x-x + √x -1 = 1/2 √4x-x + 4
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Toán Lớp 9: Giải ptrinh:
c) 3 √x+2 √9x = 5 √4x – 2
d) √9x-x + √x -1 = 1/2 √4x-x + 4
Comments ( 1 )
a)Dkxd:x \ge 0\\
3\sqrt x + 2\sqrt {9x} = 5\sqrt {4x} – 2\\
\Leftrightarrow 3\sqrt x + 2.3\sqrt x = 5.2\sqrt x – 2\\
\Leftrightarrow 10\sqrt x – 3\sqrt x – 6\sqrt x = 2\\
\Leftrightarrow \sqrt x = 2\\
\Leftrightarrow x = 4\left( {tmdk} \right)\\
Vậy\,x = 4\\
d)Dkxd:x \ge 1\\
\sqrt {9x – 9} + \sqrt {x – 1} = \dfrac{1}{2}\sqrt {4x – 4} + 4\\
\Leftrightarrow 3\sqrt {x – 1} + \sqrt {x – 1} = \dfrac{1}{2}.2\sqrt {x – 1} + 4\\
\Leftrightarrow 3\sqrt {x – 1} = 4\\
\Leftrightarrow \sqrt {x – 1} = \dfrac{4}{3}\\
\Leftrightarrow x – 1 = \dfrac{{16}}{9}\\
\Leftrightarrow x = \dfrac{{25}}{9}\left( {tmdk} \right)\\
Vậy\,x = \dfrac{{25}}{9}
\end{array}$