0.2x + 0.5y= 0.2 4 x + y= 4-搜答案-智慧作业帮

令a=x+2yb=3x-ya/2+b/3=5(1)0.2a+0.8b=4(2)所以a=20-4b代入(1)10-2b+b/3=55b/3=5b=3a=20-4b=8所以x+2y=8(3)3x-y=3(

0.2x平方y-0.5xy平方-0.3x平方y+0.7x平方y,=0.2x²y-0.5xy²-0.3x²y+o.7x²y,=0.2x²y-0.3x&#

y=(lnX)/x-x

x=1时,最大值-1

先对原式化简,0.2X^2Y-0.5XY^2-0.3X^2Y+0.7X^2Y=（0.2-0.3+0.7）X^2Y-0.5XY^2=0.6X^2Y-0.5XY^2=XY（0.6X-0.5Y）,然后将X,

p(x+y)=PX+PY-P(XY)因为独立P(XY)=PXPYPX=0.5带入上式0.7=0.5+PY-0.5PY0.5PY=0.2PY=0.4再问：再问你一道，E(x)3,E(2x-3)=?再答：

x+y=5; x^y+y^x=17

X=2,Y=3或X=3,Y=2

由题,y*x/30000000+0.18x=-y*x/30000000-0.5x2y*x/30000000=-0.68x1)x=0,等式成立2）x不等于0,y=-10200000

symsxyeq=cos(x*y)*cos(x*(1-y))-0.5*x*sin(x*y)*sin(x*(1-y))-1;ezplot(eq)

1.先化简,再求值:(2X+Y)^2-(2X-Y)(X+Y)-2(X-2Y)(X+2Y),其中X=0.5,Y=-2原式=4x^2+4xy+y^2-(2x^2+2xy-xy-y^2)-2(x^2-4y^

先一个一个的展开括号项,再同项合并就行了啊[x(x-y)-y(x-y)+(x+y)(x-y)]÷2x=[xx-xy-(xy-yy)+x(x-y)+y(x-y)]÷2x=[xx-xy-xy+yy+xx-

0.58=(0.5x+0.7y)/(x+y)0.58(x+y)=0.5x+0.7y0.58x+0.58y=0.5x+0.7y0.58x-0.5x=0.7y-0.58y0.08x=0.12yx：y=0.

0.58=(0.5x+0.7y)/(x+y)0.58(x+y)=0.5x+0.7y0.08x=0.12yx/y=0.12/0.08=3/2

0.5x+0.7y=35x+0.4y=40化简,得5x+7y=350①5x+2y=200②①－②,得5y=150y=30将y=30代入①,得x=28.

(lim) x/x-y=

你这个题目存在很多问题,(lim)x/x-y是X除以X在减去Y呢,还是除以（X-Y）这个整体啊,细节问题啊,值得注意.如果我猜的没错的话,答案应该是1再问：(LIM)X→0Y→0再答：还是1

x+y=1270.5x+0.8y=83x+1.6y=166下面等式减上面得：0.6y=39y=65,x=62

对x求导0.5*1/(x²+y²)*(x²+y²)'=1/[1+(y/x)²]*(y/x)'0.5/(x²+y²)*(2x+2y*

（0.2x+0.1y）/2-（4x-y）/10=（x-y）/5+(3x+0.5y)/30①(3x+2y-1)/8=3-(0.8x-5y)/41②①两边同时乘以60得（6x+3y）-（24x-6y）=（

(3x+2y)/(6x-5y)

y=2x^2-4x-8=2(x²-2x)-8=2(x-1)²-10y=0.5x^2+2x-1=0.5(x²+4x)-1=0.5(x+2)²-3

假设：X=Y/XY=X/Y带入函数就是：F(y/x,x/y)=（y/x+x/y）/(y/x—x/y)=x²+y²)/(y²-x²)希望可以帮助你!