求函数f(x,y)=x2+xy+y2-6x-3y的极致
来源:学生作业帮 编辑:搜搜做题作业网作业帮 分类:数学作业 时间:2024/06/22 23:24:31
求函数f(x,y)=x2+xy+y2-6x-3y的极致
![求函数f(x,y)=x2+xy+y2-6x-3y的极致](/uploads/image/z/7947158-14-8.jpg?t=%E6%B1%82%E5%87%BD%E6%95%B0f%28x%2Cy%29%3Dx2%2Bxy%2By2-6x-3y%E7%9A%84%E6%9E%81%E8%87%B4)
分别对x,y求偏导数得:
f'(x)=2x+y-6
f'(y)=2y+x-3
令两者都为0,解得驻点为:(3,0)
又分别对其求二阶偏导数:
f''(x)=2 =A
f''(y)=2 =C
用f'(x)再对y求偏导数得:
f''(x,y)=1 =B
由极值的判别式可得:
[f''(y)]^2 - [f''(x)].[f''(x,y)]=B^2 - A.C
=1-4=-30,故在(3,0)这点取得极小值:
f(x,y)极小=f(3,0)
=9-18=-9
f'(x)=2x+y-6
f'(y)=2y+x-3
令两者都为0,解得驻点为:(3,0)
又分别对其求二阶偏导数:
f''(x)=2 =A
f''(y)=2 =C
用f'(x)再对y求偏导数得:
f''(x,y)=1 =B
由极值的判别式可得:
[f''(y)]^2 - [f''(x)].[f''(x,y)]=B^2 - A.C
=1-4=-30,故在(3,0)这点取得极小值:
f(x,y)极小=f(3,0)
=9-18=-9
求函数f(x,y)=x2+xy+y2-6x-3y的极致
已知2x=3y,求xy/(x2+y2)-y2/(x2-y2)的值
求函数f(x,y)=(x2+y2)2-2(x2-y2)的极值
若X2+Y2-2X-6Y+10=0 ,求(x2-y2)/xy的值
已知x≠y ,x2-x=3 ,y2-y=3 ,求代数式x2+xy+y2 的值.
x(x-1)-(x2-y)=-3,求x2-y2-2xy的值
x(x-1)-(x2-y)=-3,求x2+y2-2xy的值
已知x(x-1)-(x2-y)=-3,求x2+y2-2xy的值
正整数x,y满足x2-y2=2xy,求x-y/x+y的值
整数x,y满足x2-y2=2xy,求x-y/x+y的值
已知X2+Y2+8X+6Y+25=0 求代数式X2++XY+4Y2分之X2-4Y2 减X+2Y分之X的值
若函数f(x)对任意实数x,y均有f(x+y)=2f(y)+x2+2xy-y2+3x-3y,则f(x)的解释式为____