1. want, require, worth(形容词)后面接doing也可以表示被动意义。
Your hair wants cutting
The book is worth reading
The floor requires washing.
2.need既可以用need to be done 也可以使用need doing ，两种形式都表达被动的意义
The house needs painting= the house needs to be painted.
The watch needed repairing= the watch needed to be repaired.
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