字1~9被填入到下面3×3的方格中,其中每个数字都恰好被用了一次.如果在方格的右边和下边所写的数字代表的是该行或该列中所填数的乘积,则在“*”格中所填的数字应该是____ .
如图所示,A为固定在车上的超声波发射装置,B为障碍物.小车以速度v向右做匀速直线运动,经过定点P时,A水平向右发射一超声波信号,信号遇到障碍物后立即反向弹回.已知超声波在空中的传播速度不变,与小车相遇后被吸收而不反弹.设超声波遇到障碍物、小车时,小车与障碍物间的距离分别为x1、x2.则选项中描述x1、x2随小车速度v变化的关系图象中,可能正确的是( )
There will be many changes in our life in the future. We will____ flying cars to work. We will travel to ____ . Maybe we will ____ live in space. Students won't ____ schoolbags to go to school any more. They will learn on ____ at home. And there will be robots in our home. The robots will help us do all the housework. Life will be great at that time.
I'd like to eat out, but, ________, I should be trying to save money.