A:1
B:2
C:3
D:4
已知点P(x,y)满足条件y≤xx+y≤1y≥-1,则目标函数z=2x﹣y的最大值为____ .
— Miss Liu, when did you come here?
— In 2015. I here for two years.
湘江里所有的生物与它的生活环境一起构成了( )