worth 是形容词.worth studying 作 subject 的定语.要用worthy 就应该是 worthy of being studied .
worth 的用法基本是
be worth + doing eg The book is well worth reading .
be worth + 名词 （ 钱数 ） eg.The necklace is worth 3000 yuan .
worthy 也是形容词,其基本结构是：
be worthy of being done eg.The book is worthy of being read .
be worthy to be done .eg .The place is worthy to be visited .
be worthy of + n eg .He is worthy of the praise .