Find the following limits.
\lim\limits_{x \to 3} f\left(x\right) when f(x)=\left(\dfrac{2}{7}\right) ^x
\lim\limits_{x \rightarrow -\infty}f\left(x\right) when f(x)=(3)6^{-x}
\lim\limits_{x \rightarrow \infty} f\left(x\right) when f(x)=2^{\frac{1}{4x}}
\lim\limits_{x \rightarrow 3} f\left(x\right) when f(x)=2\left(\dfrac{2}{5}\right)^x
\lim\limits_{x \rightarrow \infty} f\left(x\right) when f(x)=\dfrac{3^{2x}-1}{3^x}
\lim\limits_{x \rightarrow -\infty} f\left(x\right) when f(x)=\dfrac{3^x}{2^x}
\lim\limits_{x \rightarrow \infty} f\left(x\right) when f(x)=\dfrac{4^x}{5^x}