计算机技术和()是变频器发展的支柱。
参考答案:自动控制理论
已知x1、x2为方程x2+5x+2=0的两实根,则x13+23x2+5= _________ .
Since the fire is increasing on board the vessel,the Captain orders that the ship be().
A.subtle
B.dental
C.brittle
D.scuttled