a) \( \lim{ (-1)^n \left( \frac{3n+5}{3n+1} \right)^n } = ?\)
b) \( \lim{ \left( \frac{5-2n}{1+2n} \right)^{n-7} } = ?\)
c) \( \lim{ \left( \frac{3-2n}{5-2n} \right)^{n+6} } = ?\)
d) \( \lim{ \left( \frac{12n+n^2}{2n+n^2} \right)^{ \frac{n-5}{2} } } = ?\)
e) \( \lim{ \left( \frac{n-2n^2}{7n+2n^2} \right)^{n-12} } = ?\)
f) \( \lim{ \left( \frac{2n^2+7}{2n^2-5} \right)^{n^2} } = ?\)
