Question

Rút gọn

\(B=\left(\dfrac{x^3}{x^4-4x^2}+\dfrac{12}{12-6x}+\dfrac{1}{x+2}\right):\left(\dfrac{10-x^2}{x+2}+x-2\right)\)

Answer 1

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Answer 2

\(=\left[\dfrac{x^3}{x^2\left(x^2-4\right)}+\dfrac{12}{6\left(2-x\right)}+\dfrac{1}{x+2}\right]:\left(\dfrac{10-x^2}{x+2}+x-2\right)\)

\(=\left[\dfrac{x}{\left(x-2\right)\left(x+2\right)}-\dfrac{2}{x-2}+\dfrac{1}{x+2}\right]:\left(\dfrac{10-x^2}{x+2}+x-2\right)\)

\(=\dfrac{x-2x-4+x-2}{\left(x-2\right)\left(x+2\right)}:\left(\dfrac{10-x^2}{x+2}+x-2\right)\)

\(=-\dfrac{6}{\left(x-2\right)\left(x+2\right)}:\dfrac{10-x^2+x^2+2x-2x-4}{x+2}\)

\(=-\dfrac{6}{\left(x-2\right)\left(x+2\right)}.\dfrac{x+2}{6}\)

\(=\dfrac{-1}{x-2}\)