28 tháng 2 2022 lúc 20:43
Bài 3:
a: ĐKXĐ: \(x\notin\left\{0;6;-6;3\right\}\)
b: \(A=\left(\dfrac{x}{\left(x-6\right)\left(x+6\right)}-\dfrac{x-6}{x\left(x+6\right)}\right):\dfrac{2\left(x-3\right)}{x\left(x+6\right)}-\dfrac{x}{x-6}\)
\(=\dfrac{x^2-x^2+12x-36}{x\left(x-6\right)\left(x+6\right)}\cdot\dfrac{x\left(x+6\right)}{2\left(x-3\right)}-\dfrac{x}{x-6}\)
\(=\dfrac{12x-36}{x-6}\cdot\dfrac{1}{2\left(x-3\right)}-\dfrac{x}{x-6}\)
\(=\dfrac{12\left(x-3\right)}{2\left(x-3\right)\left(x-6\right)}-\dfrac{x}{x-6}\)
\(=\dfrac{6-x}{x-6}=-1\)
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