不用被动语态.
这种前面有形容词,表宾补的不定式不用被动,但可表示被动关系,例：
The question is easy to work out.
而不说：the question is easy to be worked out.
The book is difficult to understand.
而不说The book is difficult to be understood.
这种句子并不是被动结构,所以不需要用被动语态.