8.设f(x,y,z)=xy^2+yz^2+zx^2,求f_(xx)(0,0,1),f_(xz)(1,0,2),f_(yz)(0,-1,0)及f_(mx)(2,0,1).

1.设f(x,y)=e^sqrt(x^(2)+y^{4)},求f_(x)(0,0),f_(y)(0,0).1.设$f(x,y)=e^{\sqrt{x^{2}+y

双曲线C:(x^2)/(a^2)-(y^2)/(b^2)=1(a>0,b>0)的左、右焦点分别是F_(1),F_(2)，左、右顶点分别为A_(1),A_(2)，

设函数 z = f(x, y) 在 (x_0, y_0) 具有二阶连续的偏导数，f_x(x_0, y_0)= f_y(x_0, y_0)= 0，f_(xx)(x

设f（x,y,z）=^2+2(y)^2+3(z)^2+xy+3x-2y-6z,求grad f(0, 0, 0) 及grad f(1, 1, 1)设f（x,y,z

设f(x,y)=e^-xsin(x+2y)，则f_(x)(0,(pi)/(4))=____7. (5.0分) 设$f(x,y)=e^{-x}\sin(x+2

函数z=f(x,y)在P(x_(0),y_(0))处一定有f_(xy)(x_(0),y_(0))=f_(yx)(x_(0),y_(0)).A 对B 错A. 对B

设二维随机变量(X,Y)的联合概率密度为f(x,y)=}2x,0le xle 1,0le yle 1,0,其他,求Z=X+Y的概率密度f_(Z)(z).解：f_

8、设(x,y,z)=(x)^2+2(y)^2+3(z)^2+xy+3x-2y-6z，求grad f(0,0,0)及grad f(1,1,1).8、设，求gra

已知F_(1)，F_(2)分别为椭圆C: (x^2)/(16)+(y^2)/(b^2)=1(b>0)的左、右焦点，P(2,3)为C上一点，则△PF_(1)F_(

2.设F_(1)(x),F_(2)(x)是区间I内连续函数f(x)的两个不同的原函数，且f(x)≠0，则在区间I内必有( ).A. $F_{1}(x)+F_{2