若3a2-a-2=0，则-6a2+2a=______．
由3a2-a-2=0，得3a2-a=2，
∴-6a2+2a=-2（3a2-a）=-2×2=-4．
Cao Cao’s tomb is reported ______ in China, which attracts nationwide attention.
A．being found
B．to be found
C．having been found
D．to have been found
标准麻花钻主切削刃在外径边缘处前角约为（）。
A.－10°
B.10°
C.20°
D.30°
