Toán Lớp 8: (1/x^2-9+2/3-x+3/x+3):x-14/x+3
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Toán Lớp 8: (1/x^2-9+2/3-x+3/x+3):x-14/x+3
Comments ( 1 )
Dkxd:\left\{ \begin{array}{l}
x\# 14\\
x\# 3\\
x\# – 3
\end{array} \right.\\
\left( {\dfrac{1}{{{x^2} – 9}} + \dfrac{2}{{3 – x}} + \dfrac{3}{{x + 3}}} \right):\dfrac{{x – 14}}{{x + 3}}\\
= \left( {\dfrac{1}{{\left( {x – 3} \right)\left( {x + 3} \right)}} – \dfrac{2}{{x – 3}} + \dfrac{3}{{x + 3}}} \right).\dfrac{{x + 3}}{{x – 14}}\\
= \dfrac{{1 – 2\left( {x + 3} \right) + 3\left( {x – 3} \right)}}{{\left( {x + 3} \right)\left( {x – 3} \right)}}.\dfrac{{x + 3}}{{x – 14}}\\
= \dfrac{{1 – 2x – 6 + 3x – 9}}{{x – 3}}.\dfrac{1}{{x – 14}}\\
= \dfrac{{x – 14}}{{x – 3}}.\dfrac{1}{{x – 14}}\\
= \dfrac{1}{{x – 3}}
\end{array}$