why not 后面+let sb do还是to let sb do?

why not 后面+let sb do还是to let sb do? let sb.do sth.该否定句是let sb.not do sth.还是let sb.not to do sth let sb to do 还是let sb do let sb do sth还是let sb to do sth why not sb +do还是to do let sb not do sth 关于let句型是let sb do sth还是let sb to do sth not let sb do sth 还是 let sb not do sth let sb do 为什么不是let sb to do? let sb.do sth.or let sb.to do sth letlet sb do sth句型,怎么变否定句?let sb not do sth还是let sb don‘t do let 的用法 是let sb.not do sth.還是let sb not to do sth.