Toán Lớp 8: 2x/x+1+x-1/x-3x^2-2x-1/x^2+x
a) rút gọn
b) tìm x để a= 1/2
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Toán Lớp 8: 2x/x+1+x-1/x-3x^2-2x-1/x^2+x
a) rút gọn
b) tìm x để a= 1/2
Comments ( 1 )
a)A = \dfrac{2}{{x + 1}}\\
b)x = 3
\end{array}\)
a)DK:x \ne \left\{ { – 1;0} \right\}\\
A = \dfrac{{2x}}{{x + 1}} + \dfrac{{x – 1}}{x} – \dfrac{{3{x^2} – 2x – 1}}{{{x^2} + x}}\\
= \dfrac{{2{x^2} + \left( {x – 1} \right)\left( {x + 1} \right) – 3{x^2} + 2x + 1}}{{x\left( {x + 1} \right)}}\\
= \dfrac{{ – {x^2} + {x^2} – 1 + 2x + 1}}{{x\left( {x + 1} \right)}}\\
= \dfrac{{2x}}{{x\left( {x + 1} \right)}} = \dfrac{2}{{x + 1}}\\
b)A = \dfrac{1}{2}\\
\to \dfrac{2}{{x + 1}} = \dfrac{1}{2}\\
\to x + 1 = 4\\
\to x = 3
\end{array}\)