A:
B:
C:
D:
解二元一次方程组: {3x+2y=192x−y=1 .
下列现象是由于地球不停地自转而产生的( )
Nanjing, the ancient capital of the six dynasties, is becoming ________ international city and attracts more and more foreign tourists every year.
若函数fx=1+3x+a·9x,其定义域为(-∞,1,则a的取值范围是( )