Toán Lớp 8: e,1/x+5+2/x-5-2x+10/x^2-25
f,2x+6/3x^2-x: x^2+3x/1-3x
tính help me
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Toán Lớp 8: e,1/x+5+2/x-5-2x+10/x^2-25
f,2x+6/3x^2-x: x^2+3x/1-3x
tính help me
Comments ( 1 )
e)\dfrac{1}{{x + 5}} + \dfrac{2}{{x – 5}} – \dfrac{{2x + 10}}{{{x^2} – 25}}\\
= \dfrac{{x – 5 + 2\left( {x + 5} \right) – 2x – 10}}{{\left( {x + 5} \right)\left( {x – 5} \right)}}\\
= \dfrac{{x – 5 + 2x + 10 – 2x – 10}}{{\left( {x + 5} \right)\left( {x – 5} \right)}}\\
= \dfrac{{x – 5}}{{\left( {x + 5} \right)\left( {x – 5} \right)}}\\
= \dfrac{1}{{x + 5}}\\
f)\dfrac{{2x + 6}}{{3{x^2} – x}}:\dfrac{{{x^2} + 3x}}{{1 – 3x}}\\
= \dfrac{{2\left( {x + 3} \right)}}{{x\left( {3x – 1} \right)}}.\dfrac{{1 – 3x}}{{x\left( {x + 3} \right)}}\\
= \dfrac{2}{{ – x}}.\dfrac{1}{x}\\
= – \dfrac{2}{{{x^2}}}
\end{array}$