x y=3524x 18y=750
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已知x^2+xy=2,xy+y^2=1,则x^2+2xy+y^2x^2+2xy+y^2=x^2+xy+xy+y^2=2+1=3
5x²-3xy-4y²-11xy-7x²+2y²=5x²-7x²+2y²-4y²-3xy-11xy=-2x²-
根据题意得:分母:x+y+2xy=3xy+2xy=5xy分子:2x+2y-xy=2×3xy-xy=6xy-xy=5xy∴值为5xy分之5xy即为1
(3xy)平方/(-xy)+(x-2y)平方-(x+2y)(x-2y)=-9xy+(x-2y)(x-2y-x-2y)=-9xy+(x-2y)(-4y)=-9xy-4xy+8y²=8y
2x+y+6≥6+2√2xyxy≥6+2√2xy(√xy-√2)^2≥8√xy-√2≥2√2或√xy-√2≤-2√2(不可能)所以xy最小值是(3√2)^2=18-------------------
由题设可知y=xy-1,∴x=yx3y=x4y-1,∴4y-1=1,故y=12,∴12x=x,解得x=4,于是x+y=4+12=92.故答案为:92.
(x+1)平方+y-1的绝对值=0所以:x+1=0,且y-1=0所以x=-1,y=12(xy-5xy平方)-(3xy平方-xy)=2xy-10xy-3xy+xy=3xy-13xy=3*(-1)*1-1
平方和绝对值都大于等于0,相加等于0,若有一个大于0,则另一个小于0,不成立.所以两个都等于0所以x+1=0,y-1=0x=-1,y=1所以原式=2xy-2xy²-3xy²+xy=
∵xy=2,∴x=2y,则原式=(2y)2−2y•y+3y2(2y)2+2y•y+6y2=4y2−2y2+3y24y2+2y2+6y2=512.
不是含有两个未知数,并且含有未知数的项的最高次数是二的整式方程,叫做二元二次方程二元二次方程的应用.其一般式为: Ax²+Bxy+Cy²+Dx+Ey+F.(a、b、c、d、e、f
10x+y-(10y+x)=x9x-9y=x8x=9yx=9,y=8xy=98
4x²+8xy+9y²=2(2x²+xy)+3(3y²+2xy)=38.
由xy=3,得到x=3y,则原式=9y2+6y2−3y29y2−3y2+y2=127.
x²-2xy+y²=x²-3xy+xy+y²=-5+3=-2
由xy=27得,x=27y,∴x2−3xy+2y22x2−3xy+7y2=449y2−67y2+2y2849y2−67y2+7y2=60309=20103.故选C.
这类题,先化简代数式为XY与X+Y的代数式,然后代入已知条件,就可以算出来.(3xy+10y)+[5x-(2xy+2y-3x)]=3XY+10Y+5X-2XY-2Y+3X=XY+8Y+8X=XY+8(
(3x-2y+8xy)-(x-4y-5xy)=3x-2y+8xy-x+4y+5xy=(3x-x)+(-2y+4y)+(8xy+5xy)=2x+2y+13xy=2(x+y)+13xy=2×3+13×(-
xy'+y=xy^3(xy)'=xy*y^2令xy=u,y=u/x原式化为u'=u*(u/x)^2即du/u^3=dx/x^2两边对x积分得-1/2*1/u^2=-1/x+C1即1/(xy)^2=2/
两边微分:d(xy)+dcosy-dsinx=0ydx+xdy-sinydy-cosxdx=0dy=(cosx-y)dx/(x-siny)
xy²-2xy+2y-4=xy(y-2)+2(y-2)=(y-2)(xy+2)