Question

Answer 1

Rút gọn biểu thức:

\(\left(\dfrac{1}{x^2-8x+16}-\dfrac{1}{x^2-16}\right):\left(3-\dfrac{12}{x+4}\right)\)

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

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

\(=\left(\dfrac{x+4-x+4}{\left(x+4\right)\left(x-4\right)^2}\right).\dfrac{x+4}{3x}\)

\(=\dfrac{8\left(x+4\right)}{3x\left(x+4\right)\left(x-4\right)^2}\)

\(=\dfrac{8}{3x\left(x-4\right)^2}\)

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