\(D=\dfrac{x-2}{x+2}.\left(\dfrac{5x+10}{7x-14}+\dfrac{x-2}{3x-6}\right)+\dfrac{3x^2-12}{2x^2-8x+8}\)
\(D=\dfrac{x-2}{x+2}.\left(\dfrac{5\left(x+2\right)}{7\left(x-2\right)}+\dfrac{x-2}{3\left(x-2\right)}\right)+\dfrac{3\left(x^2-4\right)}{2\left(x^2-4x+4\right)}\)
\(D=\dfrac{x-2}{x+2}.\dfrac{5\left(x+2\right)}{7\left(x-2\right)}+\dfrac{x-2}{3\left(x-2\right)}.\dfrac{x-2}{x+2}+\dfrac{3\left(x^2-4\right)}{2\left(x^2-4x+4\right)}\)
\(D=\dfrac{5}{7}+\dfrac{x-2}{2\left(x+2\right)}+\dfrac{3\left(x-2\right)\left(x+2\right)}{2\left(x-2\right)^2}\)
\(D=\dfrac{5}{7}+\dfrac{x-2}{2\left(x+2\right)}+\dfrac{3\left(x+2\right)}{2\left(x-2\right)}\)
\(D=\dfrac{5}{7}-\dfrac{-\left(x-2\right)}{2\left(x-2\right)}+\dfrac{3\left(x+2\right)}{2\left(x-2\right)}\)
\(D=\dfrac{5}{7}-\dfrac{-\left(x-2\right)+3x+2}{2\left(x-2\right)}\)
\(D=\dfrac{5}{7}-\dfrac{2x+4}{2\left(x-2\right)}\)
\(D=\dfrac{5}{7}+\dfrac{2\left(x-2\right)}{2\left(x-2\right)}=\dfrac{5}{7}+\dfrac{x-2}{x-2}\)
\(D=\dfrac{5}{7}+1=\dfrac{12}{7}\)
Vậy \(D=\dfrac{12}{7}\)
