x y 属于R x y等于5 求-搜答案-搜搜做题作业网

X+Y=5,XY=2,5X+4Y-3X-2Y+XY=2X+2Y+XY=2(X+Y)+XY=2×5+2=12.

xy^5-xy等于多少

原式=xy(y^4-1)=xy(x²+1)(x²-1)=xy(x²+1)(x+1)(x-1)

xy分之x加y等于2∴x+y=2xy3x减5xy加3y分之负x加3xy减y=[-(x+y)+3xy]/[3(x+y)-5xy]=(-2xy+3xy)/(6xy-5xy)=xy/(xy)=1

由　1/X-1/Y=5,两边同乘　XY,得出Y-X=5XY,那么　　分子　-X+XY+Y=6XY分母　2X+7XY-2Y=7XY-2(Y-X)=-3XY　　得此分式的值为－再问：还有一题x+x分之一=

因为x+y除以xy等于4,所以,x+y=4xy2x-5xy+2y=2(x+y)-5xy=2*4xy-5xy=3xyx+2xy+y=4xy+2xy=6xy所以,2x-5xy+2y除以x+2xy+y的值＝

处理这类比例问题,有一个通用方法如果：x:y:z=a:b:c可以设x=aky=bkz=ck带入计算,就行了自己来试试吧~

通分1/x-1/y=(y-x)/xy=3y-x=3xyx-y=-3xy原式=[(x-y)-2xy]/[5(x-y)+3xy]=(-3xy-2xy)/(-15xy+3xy)=-5xy/(-12xy)=5

1)(x^2+y^2-xy)'=(1)'有2x+2yy'-y-xy'=0令y'=-1有2x-2y-y+x=0有x=yx=y=+_1-2

那就会等于-7X+5(X+Y)-3xy-10y=5(x+y)-10XY-10Y=5(x-y-2xy)=-35再问：7X去哪里了，10xy那一步没看懂再答：打错了，应该是-7XY+5(X+Y)-3xy-

1/x-1/y=5通分(y-x)/xy=5y-x=5xyx-y=-5xy原式=[3(x-y)+5xy]/[(x-y)-3xy]=(-15xy+5xy)/(-5xy-3xy)=-10xy/(-8xy)=

1/x-1/y=3y-x=3xyx-y=-3xy(5x-xy-5y)/(x-xy-y)=(-15xy-xy)/(-3xy-xy)=4

x分之1减y分之1等于31/x-1/y=3(y-x)/xy=3y-x=3xy所以x-xy-y分之5x-xy-5y=（-3xy-xy）分之(-15xy-xy)=-4分之（-16）=4

x^2+y^2=4,设x=2cosa,y=2sina,则x^2-2√3xy-y^2=4(cosa)^2-8√3cosasina-4(sina)^2=4cos2a-4√3sin2a=8cos(2a+60

5x5-3x4=13再问：怎么来的再答：(x+y)的平方减去4xy就等于x-y的平方再问：不明白再答：x+y的平方等于x平方加上y平方加上2xyx-y的平方等于x平方加上y平方减去2xy用数学语言列出

已知xy/(x+y)=2,求:(3x-5xy+3y)/(-x+3xy-y)xy/(x+y)=2得：xy=2(x+y)(3x-5xy+3y)/(-x+3xy-y)=(3x-9xy+3y+4xy)/(-x

6X^2-5XY-6Y^2=0(2X-3Y)(3X+2Y)=012X-3Y=0X=3Y/223X+2Y=0X=-2Y/3

x^2y+xy^2=xy(x+y)=6×5=30

其实这个很好理解（X-y）²=x²-2xy+y²因为已知告诉你的是X+y=5和XY=3那么我们只有想办法把（X-y）²=x²-2xy+y²写

-xy+xy等于多少?

得0=(-X+X)y=0×y=0