$$ \lim_{x \rightarrow a} f(x) \pm g(x)= \lim_{x \rightarrow a} f(x)\pm \lim_{x \rightarrow a} g(x)$$
$$=0 \pm 0=?$$
$$= \infty \pm \infty =?$$
$$= L_{1} \pm L_{2} =?$$
$$=0 \pm \infty =?$$
$$= \infty \pm0=?$$
$$=L \pm \infty =?$$
$$= \infty \pm L=?$$
$$=0 \pm L=?$$
$$=L \pm0=?$$