Toán Lớp 8: A=2+x/2-x-4x^2/x^2-4-2-x/2+x
a) dieu kien dc xac dinh cua A
b) tim x de A= -3
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Toán Lớp 8: A=2+x/2-x-4x^2/x^2-4-2-x/2+x
a) dieu kien dc xac dinh cua A
b) tim x de A= -3
Comments ( 1 )
a) – \dfrac{{4x}}{{x – 2}}\\
b)x = – 6
\end{array}\)
a)DK:x \ne \pm 2\\
A = \dfrac{{2 + x}}{{2 – x}} – \dfrac{{4{x^2}}}{{{x^2} – 4}} – \dfrac{{2 – x}}{{2 + x}}\\
= \dfrac{{ – {{\left( {2 + x} \right)}^2} – 4{x^2} – \left( {2 – x} \right)\left( {x – 2} \right)}}{{\left( {x – 2} \right)\left( {x + 2} \right)}}\\
= \dfrac{{ – 4 – 4x – {x^2} – 4{x^2} + {x^2} – 4x + 4}}{{\left( {x – 2} \right)\left( {x + 2} \right)}}\\
= \dfrac{{ – 4{x^2} – 8x}}{{\left( {x – 2} \right)\left( {x + 2} \right)}}\\
= \dfrac{{ – 4x\left( {x + 2} \right)}}{{\left( {x – 2} \right)\left( {x + 2} \right)}}\\
= – \dfrac{{4x}}{{x – 2}}\\
b)A = – 3\\
\to – \dfrac{{4x}}{{x – 2}} = – 3\\
\to \dfrac{{4x}}{{x – 2}} = 3\\
\to 4x = 3x – 6\\
\to x = – 6
\end{array}\)