\(a,A=\dfrac{\left(x^3+1\right)\left(x+1\right)}{x^4-x^3+x^2+x^2-x+1}\\ A=\dfrac{\left(x+1\right)^2\left(x^2-x+1\right)}{\left(x^2-x+1\right)\left(x^2+1\right)}=\dfrac{\left(x+1\right)^2}{x^2+1}\\ b,\left\{{}\begin{matrix}\left(x+1\right)^2\ge0\\x^2+1\ge1>0\end{matrix}\right.\Leftrightarrow A\ge0,\forall x\)