函数的驻点怎么求?答:f'x=(6-2x)(4y-y²)=0, 得x=3, 或y=0, 4f'y=(6x-x²)(4-2y)=0, 得x=0, 6, 或y=2 得驻点(3, 2), (0,0) , (0, 4), (6, 0), (6, 4)A=f"xx=-2(4y-y²)B=f"xy=(6-2x)(4-2y)=4(3-x)(2-y)C=f"yy=-2(6x-x²)在(3...
f(x)=2-2x-8的驻点是?答:f'x=(6-2x)(4y-y²)=0, 得x=3, 或y=0, 4f'y=(6x-x²)(4-2y)=0, 得x=0, 6, 或y=2 得驻点(3, 2), (0,0) , (0, 4), (6, 0), (6, 4)A=f"xx=-2(4y-y²)B=f"xy=(6-2x)(4-2y)=4(3-x)(2-y)C=f"yy=-2(6x-x²)在(3...
高等数学,请问一下这个二元函数极值怎么算?答:f = x^2+y^2-2x+2y-11,fx = 2x-2, fy = 2y+2, 得唯一驻点 (1, -1)A = fxx = 2, B = fxy = 0, C = fyy = 2 AC - B^2 > 0 , A > 0, (1, -1) 是极小值点,极小值 f(1, -1) = -13.
求二元函数z=3(x+y)-x^3-y^3的极值点?答:Z'x=3-3x^2 ,Z'y=3-3y^2 令 3-3x^2=0 3-3y^2=0 解方程组得函数的驻点为 (1,1),(1,-1),(-1,1),(-1,-1)A=Z''xx=-6x C=Z''yy=-6y B=Z''xy=0 将驻点坐标代入上面的A.B C然后利用判别式 B^2-AC与0的大小关系,得出驻点是不是极值点,8,