The solution to the answer is the usual solution. Set two coordinates, and then list the linear equation according to the tangency condition, from which the relationship between X 1 and X2 can be solved.

This big topic is to master the general method, that is, the general method. No matter how the topic changes, set a point, "decide without seeking"!

I hope it will help you understand.

I am a college entrance examination student this year.