Compute the following limits using l'H\^opital's rule if appropriate. Use INF to denote $\infty$ and MINF to denote $-\infty$.

$\displaystyle \lim_{x\to 0} \frac{1-\cos(7 x)}{1-\cos(3 x)}$ =

$\displaystyle \lim_{x\to 1} \frac{4^x-3^x -1}{x^2-1}$ =