Neil seemed very calm, yet Celia was still aware of his panic _______ the surface.
A:beneath
B:over
C:beyond
D:from
菱形OACB在平面直角坐标系中的位置如图所示,点C的坐标是(6,0),点A的纵坐标是1,则点B的坐标是( )
已知f(x)=2x2﹣tx,且|f(x)|=2有且仅有两个不同的实根α和β(α<β).
(1)求实数t的取值范围
(2)若x1、x2∈α,β且x1≠x2,求证:4x1x2﹣t(x1+x2)﹣4<0;
读美国示意图回答下列问题。