I was late for school this morning because the traffic was ________ by an accident. ( )
A:used up
B:given up
C:locked up
D:held up
(Ⅰ)求椭圆C的方程;
(Ⅱ)设另一直线l与椭圆C交于A,B两点,原点O到直线l的距离为 32 ,求△AOB面积的最大值.
解方程组3x-y+2z=32x+y-4z=117x+y-5z=1,若要使运算简便,消元的方法应选取( )
如图所示,请将螺线管、滑动变阻器接入电路中,使开关闭合后,螺线管与条形磁铁相互排斥,滑动变阻器滑片P向右移动会使斥力变大。