\(x^2\equiv1\left(mod\text{ }x^2-1\right)\Rightarrow x^{2018}=\left(x^2\right)^{1009}\equiv1^{1009}\equiv1\left(mod\text{ }x^2-1\right);x^{2019}\equiv x\left(mod\text{ }x^2-1\right)\Rightarrow x^{2019}+x^{2018}+x+2018\equiv1+x+x+2018\equiv2x+2019\left(mod\text{ }x^2-1\right)\)