— May we leave the classroom now?
— No, you ________. You ________ to leave until the bell rings.
设月球绕地球运动的周期为27天,则地球的同步卫星到地球中心的距离r与月球中心到地球中心的距离R之比 为()
已知偶函数f(x)在(0,+∞)上为减函数,且f(2)=0,则不等式fx+f-xx>0的解集为____