Question: Is there a line in the xyXY plane that has all rational coordinates. Prove your answer.
Idea: There is most certainly not. I believe it can be shown that between any 2 rational points that there is at least one rationalirrational coordinate. Therefore, there can not be a line that contains only rational points. The issue is that I am not sure how to show this. Any ideas? I am also open to any other ideas of how to do this. Thanks.
Note: this is for an intro to proofs study guide. So, I would prefer not to use advanced theorems.