\(a,\Leftrightarrow A=\dfrac{8x^3y^4}{2x^3y^2}=4y^2\\ b,\Leftrightarrow A=\dfrac{\left(x+1\right)\left(x+2\right)}{\left(x^2-1\right)\left(x+2\right)}\\ \Leftrightarrow A=\dfrac{\left(x+1\right)\left(x+2\right)}{\left(x-1\right)\left(x+1\right)\left(x+2\right)}=\dfrac{1}{x-1}\)