вычислите [tex] \frac{4}{ \sqrt{13 } -3} - \frac{9}{ \sqrt{13}-2 } [/tex]

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[tex] \frac{4}{ \sqrt{13} -3} - \frac{9}{ \sqrt{13} -2} = \frac{4( \sqrt{13} -2)}{( \sqrt{13}-3)( \sqrt{13} -2)} - \frac{9( \sqrt{13}-3) }{( \sqrt{13}-3)( \sqrt{13} -2 )} = \\ = \frac{4 \sqrt{13} -8-9 \sqrt{13} +27}{13-2 \sqrt{13}-3 \sqrt{13} +6 }= \frac{-5 \sqrt{13} +19}{-5 \sqrt{13} +19} =1[/tex]