若4x2+mx+9是完全平方式,则m的值为( )
A.12
B.-12
C.±12
D.以上都不对
∵(2x±3)2=4x2±12x+9=4x2+mx+9,
∴m=±12.
故选C.
—I regret ________ you that your application has not been successful.
—Not successful? I performed pretty well in my interview!
A.informing
B.to inform
C.having informed
D.to have informed
画出图E-20的受力图。