To show it is bounded:
0 < |(n^2 +10)/(n^3 -10)<2(n^2)/(n^2) = 2
To show it converges, try to show that the sequence is monotone, and use the fact that all bounded and monotonic sequences converge. Or, see below:
To show it converges:
[n^2(1 + 10/n^2)] / [n^2(n - 10/n^2)]
= (1 + 10/n^2) / (n - 10/n^2)
the 10/n^2 in both the numerator and denominator converge to 0 and so we have 1/n, which converges to 0 as well.