Toán Lớp 9: Giải phương trình ( tìm đkxđ)
a) $\sqrt{2x-3}$=$\sqrt{5}$
b) $\sqrt{3x-2}$=$\sqrt{12x-8}$ + $\sqrt{27x-18}$=6
c) $\sqrt{50x}$-75+$\sqrt{18x-27}$+5$\sqrt{2x-3}$=26
Leave a reply
Register Now
Login
Lost Password
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Toán Lớp 9: Giải phương trình ( tìm đkxđ)
a) $\sqrt{2x-3}$=$\sqrt{5}$
b) $\sqrt{3x-2}$=$\sqrt{12x-8}$ + $\sqrt{27x-18}$=6
c) $\sqrt{50x}$-75+$\sqrt{18x-27}$+5$\sqrt{2x-3}$=26
Comments ( 2 )
a)\sqrt {2x – 5} = \sqrt 5 \,\,\,\,DKXD:x \ge \frac{5}{2}\\
\Leftrightarrow 2x – 5 = 5\\
\Leftrightarrow 2x = 10\\
\Leftrightarrow x = 5\\
b)\sqrt {3x – 2} – \sqrt {12x – 8} + \sqrt {27x – 16} = 6\\
\Leftrightarrow \sqrt {3x – 2} – \sqrt {4\left( {3x – 2} \right)} + \sqrt {9\left( {3x – 2} \right)} = 6\\
\Leftrightarrow \sqrt {3x – 2} – 2\sqrt {3x – 2} + 3\sqrt {3x – 2} = 6\\
\Leftrightarrow 2\sqrt {3x – 2} = 6\\
\Leftrightarrow \sqrt {3x – 2} = 3\\
\Leftrightarrow 3x – 2 = 3\\
\Leftrightarrow x = \frac{{11}}{3}\\
c.\;\sqrt {50x – 75} + \sqrt {18x – 27} + 5\sqrt {2x – 3} = 26\\
\Leftrightarrow \sqrt {25(2x – 3)} + \sqrt {9(2x – 3)} + 5\sqrt {2x – 3} = 26\\
\Leftrightarrow 5\sqrt {2x – 3} + 3\sqrt {2x – 3} + 5\sqrt {2x – 3} = 26\\
\Leftrightarrow 13\sqrt {2x – 3} = 26\\
\Leftrightarrow \sqrt {2x – 2} = 2\\
\Leftrightarrow 2x – 2 = 4\\
\Leftrightarrow x = \frac{7}{2}
\end{array}\]