What did Frank and his father do yesterday?
A:They went to the library.
B:They went swimming.
C:They played chess.
如果x2+kx+1是一个完全平方式,那么k的值是____.
解方程或化简
17世纪到19世纪初,资本主义已成为世界历史发展的主流,在这一时期涌现出许多叱咤风云的政治杰出人物。下列人物属于这一时期的有( )
①克伦威尔 ②华盛顿 ③林肯 ④罗伯斯庇尔
如图△ABC中,BE平分∠ABC,DE∥BC,若DE=2AD,AE=2,那么EC=____.