Weird limit with $e^x$
HINT
Let $y=-x\to \infty$, then
$$\lim\limits_{x\to -\infty} [(x^2+1)e^x]=\lim\limits_{y\to \infty} [(y^2+1)e^{-y}]=\lim\limits_{y\to \infty} \frac{y^2+1}{e^{y}}$$
HINT
Let $y=-x\to \infty$, then
$$\lim\limits_{x\to -\infty} [(x^2+1)e^x]=\lim\limits_{y\to \infty} [(y^2+1)e^{-y}]=\lim\limits_{y\to \infty} \frac{y^2+1}{e^{y}}$$