已知x已知x
已知xY=X+1+1/X=-(|X|+1/|X)+1≤-2√[|X|*1/|X|]+1=-1,∴当且仅当|X|=1/|X|(X
x<0-x>0y=(x^2+x+1)/x =x+1+1/x-y=-x-1/x-1 >=2√[(-x)*(-1/x)] -1 =2-1 =1y<=-1所以最大值是-1