设函数f在x=0处连续，且对一切x,y有f(x+y)=f(x)+f(y).则f在R上连续，且f(x)=f(1)x....
根据f(xy)=f(x)+f(y)可以得到：f(1)=2f(1)\Rightarrow f(1)=0 2.f(x^n)=f(x^{n-1...
【题目】14.计算下列函数的偏导数:(1)z=f(u,x,y), u=xe^y 其中f具有二阶连续偏导数,求(a^2z)/(ax^3y)(2) z=f(xy,x^2+y^
对u(x,y)=x2+xy-y2∂u/∂x=2x+y,所以∂2(u)/∂x2=2∂u/∂y=x-2y,所以∂2(u)/∂y2=-2.所以∂2(u)/∂x2+∂2(u)/∂y2=0,u为调和函数设f(z)=u+iv为解析函数,则由Cauchy-Riemann方程知∂v/∂x=-∂u/∂y=-x+2y∂v/∂y=∂u/∂x=2x+...
(x,y)ne(0,0)-க்கு f(x,y)=frac{y^2-xy}{sqrtx-sqrty} எனில், lim((x,y)rarr(0,0))f(x,y)=0 என நிறுவுக.
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其他所以E(X_1)=∫_0^(+∞)x⋅ne^(-n))dx-θ)dx=∫_0^(+∞)(y+θ)⋅ne^(-xy)dy=θ+1/n E(X_1^2)=∫_0^(+∞)x^2⋅e^(-n(x-θ))dx=θ^2+2/nθ+2/(n^2) nD(X_1)=E(X_1)_1=(EX_((1)))^2=θ^2+2/nθ+2/(n^2)-(θ+1/n)^2= 方法二设 ...
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x, y, z -এর সব বাস্তব মানে f(x+y+z)=f(x)f(y)f(z)ne0 এবং f(2)=5, f’(0)=2 হলে f’(2) -এর মান হবে—