I did not use the hint, I did this instead:
\\ $a) Take some$ \ k \ $in$ \ [0,1] \ $since$ \ f \ $is continuous on$ \ [0,1] \ $then is continuous on$ \ [0,k] \ $and$ \ [k, 1] \\ $By the intermediate value theorem then$ \ f \ $takes every value in$ \ [f(0) , f(k)] \ $by the first interval and...