A function is said to have a vertical asymptote wherever the limit on the left or right (or both) is either positive or negative infinity.
For example, the function $f(x)= \frac{-15}{x^3(x+8)^4}$ has a vertical asymptote at $x=-8$.

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For each of the following limits, enter either 'P' for positive infinity, 'N' for negative infinity, or 'D' when the limit simply does not exist.
$\displaystyle{ \lim_{x\to -8^-} \frac{-15}{x^3(x+8)^4} = }$
$\displaystyle{ \lim_{x\to -8^+} \frac{-15}{x^3(x+8)^4} = }$
$\displaystyle{ \lim_{x\to -8} \frac{-15}{x^3(x+8)^4} =}$