a) \( \lim{ \frac{ \sqrt{n^2+1} + \sqrt{n^2+2n}}{ \sqrt{3n+2} + \sqrt{3n+1} } } = ? \)
b) \( \lim{ \frac{ \sqrt{n^2+1} - \sqrt{n^2+2n}}{ \sqrt{3n+2} + \sqrt{3n+1} } } = ? \)
c) \( \lim{ \frac{ \sqrt{n^2+1} - \sqrt{n^2+2n}}{ \sqrt{3n+2} - \sqrt{3n+1} } } = ? \)