已知am=3,an=9,则a3m-2n=______.
∵am=3,an=9,
∴(am)3÷(an)2=27÷81=13,
∴a3m-2n=13.
故答案为:13.
关于贫血的描述中错误的是()
A.急性贫血的症状常较显著
B.贫血症状的严重程度与贫血发生的速度和程度有关
C.老年人或伴心肺疾病者对贫血已经耐受,症状相对较轻
D.慢性贫血,由于机体对缺氧已适应,故即使贫血很重,症状也可以较轻
E.贫血是一种症状,而不是一种疾病
He had to be called two or three times he would come to his dinner.
A.before
B.when
C.until
D.as