当x=2-5,y=25时,
(x+y)(x-y)=x2-y2
=(2-5)2-(25)2
=(4-25+5)-20
=-11-25.
氧气瓶内压力达到( )Mpa,有爆炸危险。
A.100
B.1.3
C.1.5
D.150
砂仁的功效是( )
A.燥湿,发汗B.燥湿,平喘C.化湿,止呕D.化湿行气,温中止泻,安胎E.化湿,解暑