已知点P在曲线C1:x216-y29=1上,点Q在曲线C2:(x﹣5)2+y2=1上,点R在曲线C3:(x+5)2+y2=1上,则|PQ|﹣|PR|的最大值是( )
Dad is going to put____ ____ in my room.
若a>b>c,且a+2b+c=0,则ca的取值范围是____