求cov+x+y

逄邰砍2509f(x,y)=(x^2)y+y^2 求f(x+y,xy) -
逯将娥18939291378 ______ f(u,v)=(u^2)v+v^2 令u=x+y,v=xy f(x+y,xy)=[(x+y)^2]xy+(xy)^2 不要混淆表达式中的xy与所求的xy它们不是一样的

逄邰砍2509Z=e∧u sinv,而u=xy,v=x+y,求az/ax , az/ay -
逯将娥18939291378 ______ z'(x)=e^u*ysinv+e^ucosv=e^(xy)(ysin(x+y)+cos(x+y)) z'(y)=e^u*xsinv+e^ucosv=e^(xy)(xsin(x+y)+cos(x+y))

逄邰砍2509设:z=uvlnw;u=x+y,v=y - x,w=1+xy,求δz/δx. -
逯将娥18939291378 ______ u,v,w都是X,Y的函数,求δz/δx,z=uvlnw是x,y的复合函数 z=(uv)lnw z[x]=(uv)`lnw+uv(lnw)`=(u[x]v+uv[x])lnw+(uv/w)w[x] z[x],u[x],v[x],w[x]分别表示x的偏导 u[x]=1,v[x]=-1,w[x]=y 所以z[x]=(v-u)lnw+uvy/w=2xln(1+xy)+(x+y)(x-y)y/(1+xy) 麻烦采纳,谢谢!

逄邰砍2509方程3u+v+x+y+z=3的非负整数解(u,v,x,y,z)有几组? -
逯将娥18939291378 ______[答案] 21

逄邰砍2509方程2u+v+x+y+z=3的非负整数解(u,v,x,y,z)有几组?( ) -
逯将娥18939291378 ______[选项] A. 10 B. 20 C. 24 D. 30

逄邰砍2509z=(x+y)⁽¹⁺ˣʸ⁾的偏导数怎么求
逯将娥18939291378 ______ z=u^v,u=x+y,v=1+xy..∂z/∂u=vu^(v-1)=u^v,∂z/∂v=(u^v)(lnv)∂u/∂x=1,∂u/∂y=1,∂v/∂x=y,∂v/∂y=x.∂z/∂x=[∂(u^v)/∂u]∂u/∂x+[∂(u^v)/∂v]∂v/∂x =u^v+(u^v)(lnv)*y=(1+ylnv)u^v∂z/∂y=[∂(u^v)/∂u]∂u/∂y+[∂(u^v)/∂v]∂v/∂y =u^v+(u^v)(lnv)*x=(1+xlnv)u^v

逄邰砍2509设x、y、z、u和v满足下列方程组x−y+z=1(1)y−z+u=2(2)z−u+v=3(3)u−v+x=4(4)v−x+y=5(5),则yzu=______. -
逯将娥18939291378 ______[答案] (1)+(2)+(3)+(4)+(5),得 x+y+z+u+v=15(6), 由(1)+(2),得x+u=3(7), 由(2)+(3),得y+v=5(8), 由(3)+(4),得z+x=7(9), 由(4)+(5),得u+y=9(10), 又由(6)-(7)-(8),得z=7, 把z=7并代入(9),得x=0; 把...

逄邰砍2509求答案2,3要过程.急!好心人快帮忙!
逯将娥18939291378 ______ (1)V+F-E=2,V+V+8-30=2,V=12(2)V+F-E=2V=24,F=X+Y,E=24*3÷2=36V+F-E=2,24+ X+Y-36=2 所以X+Y=14

逄邰砍2509求f(xy,x/y)=(x+y)^2,求f(x,y) -
逯将娥18939291378 ______ 令u=xy,v=x/y 所以x²=uv,y²=u/v.f(u,v)=(x+y)²=x²+2xy+y² =uv+2u+u/v 所以f(x,y)=xy+2x+x/y.验证:f(xy,x/y)=xy·x/y+2xy+xy/(x/y)=(x+y)²