求E(3XY)-搜答案-搜搜考试网

3e4=2*3*4-(3+4)=24-7=1712e（3e4）=12e17=2*12*17-(12+17)=408-29=379

对x求导为y*e^(xy)对y求导为x*e^(xy)对x,y求偏导为e^(xy)+xy*e^(xy)

方程两边对x求导,得：y+xy'+y'e^y=2y+2xy'y'e^y-xy'=y得y'=y/(e^y-x)因此dy=ydx/(e^y-x)

这是离散型随机变量,得先把XY的分布律写出来,就让x和y相乘,得到分布律为xy01p1-1/n²1/n²再问：http://zhidao.baidu.com/question/43

对方程取导数y+x(dy/dx)+(dy/dx)=0(dy/dx)(x+1)=-ydy/dx=(-y)/(x+1)

xy=e^(x+y),求dx/dy

ydx/dy+x=(e^x)(e^y)dx/dy+(e^x)(e^y)dx/dy=[(e^x)(e^y)-x]/[y-(e^x)(e^y)]dx/dy=(xy-x)/(y-xy)dx/dy=x(y-1

回答：这是柯西－许瓦兹不等式(Cauchy-SchwarzInequality).证：对于任意实变量t,考虑函数q(t)=E[(X+tY)^2]=E(Y^2)t^2+2E(XY)t+E(X^2).显然

该题为隐函数求导.xy+e^(xy)=1则y+xy'+e^(xy)(y+xy')=0解得：y'=-y/x解答完毕.

左右除以x^2,y'/x+y(1/x)'=e^(x-1/x).左边就是(y/x)',两边关于x积分就能得到y=x(右边的不定积分+C).不过e^(x-1/x)不定积分没有初等函数表示啊……是不是抄错了

两边求导：e^(xy)*(xy)'-(xy)'=0e^(xy)*(y+xy')-(y+xy')=0ye^(xy)+xe^(xy)*y'=y+xy'x(e^(xy)-1)y'=y(1-e^(xy))y'

两边同时求导..得：y-e^xy(yx')=0x'=y/(ye^xy)所以dy/dx=y/(ye^xy)

siny+e^x=xy^2,两边求微分,cosydy+e^xdx=d(xy^2)cosydy+e^xdx=y^2dx+2xydy整理,得(e^x-y^2)dx=(2xy-cosy)dydy/dx=(e

e∧x+y=xy,求dy/dx

三种方法1式中同时对x求导-（y+xy‘）cosxy+2yy'=0解出y’2式中同时取微分d{sin(xy)+y^2-e^2}=dsin(xy)+dy^2-de^2=-cosxydxy+2ydy=-c

你好!两边对x求导：e^(xy)*(y+xy')-y^2=y'cosy解得y'=(y^2-ye^(xy))/(xe^(xy)-cosy)

7=xy-e^(xy),求dy/dx

如图.

两边求导得y'·e^y+(y+xy')/(xy)+e^(-x)=0

求dy/dx+y/x=e^(xy)

令e^(xy)=u,y=lnu/xDy/dx=[(x/u)*(du/dx)-lnu]/x²,∴(1/ux)*(du/dx)-lnu/x²+lnu/x²=u即du/u

答：xy=x-e^(xy)e^(xy)=x-xy=x(1-y)两边对x求导：(xy)'e^(xy)=1-y-xy'(y+xy')e^(xy)=1-y-xy'ye^(xy)+xy'e^(xy)+xy'=