The answer for the first one you have is almost correct. It is rather than .
Same deal with the second. It is not .
Those intervals can be tricky at times. If it is undefined at the endpoint, you should use the open interval. Also, always use an open interval for , as you seem to know.
Edit: forgot to add, the interval is closed in the first problem at 0 and 8 because those values make the function 0, not undefined. Since the inequality wants 0 included, the interval is closed. Hopefully that clarifies it a bit.