13: ĐKXĐ: x>=3/2
\(\sqrt{2x-3}=\dfrac{1}{2}\)
=>\(2x-3=\left(\dfrac{1}{2}\right)^2=\dfrac{1}{4}\)
=>\(2x=3+\dfrac{1}{4}=\dfrac{13}{4}\)
=>\(x=\dfrac{13}{8}\left(nhận\right)\)
14: ĐKXĐ: x>=-7/3
\(\sqrt{3x+7}=\dfrac{2}{3}\)
=>\(3x+7=\left(\dfrac{2}{3}\right)^2=\dfrac{4}{9}\)
=>\(3x=\dfrac{4}{9}-7=\dfrac{4}{9}-\dfrac{63}{9}=-\dfrac{59}{9}\)
=>\(x=-\dfrac{59}{9}:3=-\dfrac{59}{27}\left(nhận\right)\)
15: ĐKXĐ: x>=3/10
\(\sqrt{10x-3}=\dfrac{2}{5}\)
=>\(10x-3=\left(\dfrac{2}{5}\right)^2=\dfrac{4}{25}\)
=>\(10x=3+\dfrac{4}{25}=\dfrac{79}{25}\)
=>\(x=\dfrac{79}{250}\left(nhận\right)\)
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