You had better go to Beijing by train.改为否定句.（是不是 better 后加个not还是don't?）不是句中有动词要加do么,

You had better go to Beijing by train.改为否定句.（是不是 better 后加个not还是don't?）不是句中有动词要加do么,
You had better go to Beijing by train.改为否定句.（是不是 better 后加个not还是don't?）
不是句中有动词要加do么,

You had better go to Beijing by train.改为否定句.（是不是 better 后加个not还是don't?）不是句中有动词要加do么,
You had better not go to Beijing by train

you had better not go to beijing by train.

You had better not go to Beijing by train.

not 。 因为had better not do 是固定词组

You had better not go to Beijing by train