一元二次方程x2+4x+c=0有两相等实根,那么c=______.
∵一元二次方程x2+4x+c=0有两相等实根,
∴△=42-4c=0,
即-4c=-16,c=4.
根据句子意思和所给的首字母写出所缺单词。要求在答题卷上写出完整的单词。(每空只写一词)
小题1:Most people will feel h_____ when they are away from their homes for a long time.
小题2:Whether to go or not. It’s difficult for me to make a d___________.
小题3:We hope our f__________ will last forever.
小题4:He works hard every day. I think he will a_________ his ambition one day.
小题5:The student not only learn k______ from the textbooks but also from different activities.
如图所示,当条形磁铁作下列运动时,线圈中的感应电流方向应是:(从左向右看)
A.磁铁靠近线圈时,电流方向是逆时针的;
B.磁铁靠近线圈时,电流方向是顺时针的;
C.磁铁向上平动时,电流方向是逆时针的;
D.磁铁向上平动时,电流方向是顺时针的。