\(a,=\dfrac{4y\left(3-x\right)}{9}\\ b,=\dfrac{2x\left(x-2\right)-8x+2x\left(x+2\right)}{x\left(x-2\right)\left(x+2\right)}\\ =\dfrac{2x^2-4x-8x+2x^2+4x}{x\left(x-2\right)\left(x+2\right)}\\ =\dfrac{4x\left(x-2\right)}{x\left(x-2\right)\left(x+2\right)}=\dfrac{4}{x+2}\)