21a²-46ab+21b²=2012
21（a-b）²-4ab=2012
21(4n+2)²-4=2012
21(4n+2)²=2016
(4n+2)²=96
4n+2=±√96
4n=-2±4√6
n=-0.5±√6
如追加其它问题,（a-b）²为啥等于(4n+2)²a+b=4n+2a+b=4n+2 你抄错了吧 a-b=4n+2吧就是a+b=4n+221a²-46ab+21b²=201221（a+b）²-88ab=2012剩下的差不多，你自己算吧88ab对呀 21a²-46ab+21b²=201221a²+42ab-42ab-46ab+21b²=2012噢