Question

we are going to beijing by train变成否定句一般疑问句并作否定或肯定回答

Answer 1

这句话是be going to句型，变否定句时在be动词are后加not，其它不变。变一般问句时把be动词are提到句首即可。
否定句：We aren't going to Beijing
by train.
一般问句：Are we(you) going to
Beijing by train ?

Answer 2

否定句：We are not going to Beijing by train.
一般疑问句：Are you going to Beijing by train? Yes,we are
No,we are not.