Question

已知实数x,y满足2x加y大于等于1,则u=x平方加y平方加4x减2y的最小值为？急

Answer 1

u=x^2+y^2+4x-2y=(x+2)^2+(y-1)^2-5,又2x+y-1>=0,u的最小值为点（-2,1）到直线2x+y-1=0的距离的平方再减去5，为-9/5

Answer 2

2x+y≥1 u=x^2+y^2+4x-2y
=(x+2)^2+(y-1)^2-5
≥ 16/5-5=-9/5

Answer 3

负9/5