\(A=\left(\frac{x-2}{x+2}-\frac{x+2}{2-x}-\frac{x^2-3x+6}{x^2-4}\right):\left(1-\frac{3}{x-2}\right)\)
\(=\left(\frac{\left(x-2\right)^2}{\left(x+2\right)\left(x-2\right)}+\frac{\left(x+2\right)^2}{\left(x+2\right)\left(x-2\right)}-\frac{x^2-3x+6}{\left(x-2\right)\left(x+2\right)}\right)\)\(:\left(\frac{x-2}{x-2}-\frac{3}{x-2}\right)\)
\(=\frac{x^2-4x+4+x^2+4x+4-x^2+3x-6}{\left(x+2\right)\left(x-2\right)}:\frac{x-2-3}{x-2}\)
\(=\frac{x^2+3x+2}{\left(x+2\right)\left(x-2\right)}:\frac{x-5}{x-2}\)
\(=\frac{x^2+x+2x+2}{\left(x+2\right)\left(x-2\right)}:\frac{x-5}{x-2}\).
\(=\frac{x\left(x+1\right)+2\left(x+1\right)}{\left(x+2\right)\left(x-2\right)}.\frac{x-2}{x-5}\)
\(=\frac{\left(x+2\right)\left(x+1\right)}{\left(x+2\right)\left(x-2\right)}.\frac{x-2}{x-5}\)
\(=\frac{x+1}{x-2}.\frac{x-2}{x-5}\)
\(=\frac{x+1}{x-5}\)
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