抛物线与x轴交点的横坐标为-2和1,且过点(2,8),它的关系式为[ ]
A.y=2x2-2x-4
B.y=-2x2+2x-4
C.y=x2+x-2
D.y=2x2+2x-4
答案:D
They've us 150 000 dollars for the house, shall we take it? [ ]
A. provided
B. supplied
C. shown
D. offered
已知直齿圆柱齿轮全齿高h=10mm,则可求得其齿厚S等于()mm。
A.3.14
B.6.28
C.4
D.8