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$\displaystyle \begin{array}{{>{\displaystyle}l}} ( x-5)\sqrt{\frac{x}{25-x^{2}}}\\ DK\ :0< x< \ -5\ \\ -\sqrt{5-x} .\sqrt{5-x} .\frac{\sqrt{x}}{\sqrt{( 5-x)( 5+x)}}\\ \rightarrow \frac{-\sqrt{5-x} .\sqrt{x}}{\sqrt{5+x}} =\frac{-\sqrt{x}(\sqrt{( 5+x)( 5-x)}}{\left(\sqrt{5+x}\right)^{2}}\\ =\frac{-\sqrt{x} .\sqrt{25-x^{2}}}{x+5} \ \end{array}$
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