Bài 3:
a: \(=\dfrac{5\left(x+2\right)}{4\left(x-2\right)}\cdot\dfrac{-2\left(x-2\right)}{x+2}=5\cdot\dfrac{-1}{2}=\dfrac{-5}{2}\)
b: \(=\dfrac{\left(x-6\right)\left(x+6\right)\cdot\left(-3\right)}{2\left(x+5\right)\left(x-6\right)}=\dfrac{-3x-18}{2x+10}\)
c: \(=\dfrac{x+3}{\left(x-2\right)\left(x+2\right)}\cdot\dfrac{-\left(x-2\right)^3}{9\left(x+3\right)}=\dfrac{1}{9}\cdot\dfrac{-\left(x-2\right)^2}{x+2}\)
d: \(=\dfrac{-x\left(1-3x\right)}{\left(1-3x\right)^3}\cdot\dfrac{-\left(x^2-1\right)\left(x^2+1\right)}{x^2-1}\)
\(=\dfrac{1}{\left(3x-1\right)^2}\cdot\dfrac{x^2+1}{1}=\dfrac{x^2+1}{\left(3x-1\right)^2}\)