方程 x2−6x+1=0 经过配方后,其结果正确的是( )
—Why don't you get a watch for your friend as a gift?
—But it's too expensive for me _______!
张朋将连续10天引体向上的测试成绩(单位:个)记录如下:16,18,18,16,19,19,18,21,18,21.则这组数据的中位数是____.