A=X2-2XY-6Y2
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∵A=x2+xy+y2,B=-3xy-x2∴2A-3B=2(x2+xy+y2)-3(-3xy-x2)=2x2+2xy+2y2+9xy+3x2=5x2+11xy+2y2.
∵A=2x2-3xy+y2+x-3y,B=4x2-6xy+2y2+4x-y,∴a=B-2A=(4x2-6xy+2y2+4x-y)-2(2x2-3xy+y2+x-3y)=4x2-6xy+2y2+4x-y
X2+Y2+8X+6Y+25=0x²+8x+16+y²+6y+9=0(x+4)²+(y+3)²=0∴x+4=0y+3=0x=-4y=-3X2+4XY+4Y2分之
X2+Y2+8X+6Y+25=0x^2+y^2+8x+6y+25=0x^2+8x+16+y^2+6y+9=0(X+4)^2+(y+3)^2=0x=-4y=-3(x^2-4y^2)/(x^2+4xy+4
A=B+C=(2x2-3xy-y2)+(x2+xy+y2)=2x2-3xy-y2+x2+xy+y2=3x2-2xy.故选D.
你好x²+y²-10x-6y+34=0(x-5)²+(y-3)²=0每项都大于等于0,只有等于0时上式才成立,所以x=5y=3(x-y/x+y)²÷(
(1)-X2(2)-3ab-9bc+6ac(你打错了吧,应该是2ab-3bc-ac吧)(3)-4
由于(ax2-2xy+y2)-(-x2+bxy+2y2)=(a+1)x2-(2+b)xy-y2=5x2-9xy+cy2;若令上面等式成立,需满足a+1=52+b=9c=−1;解得:a=4b=7c=−1
已知2x=3y,求xy/(x^2+y^2)-y^2/(x^2-y^2)的值2x=3y-->x=(3/2)yx^2=(9/4)y^2xy/(x^2+y^2)-y^2/(x^2-y^2)==(3/2)y*
由xy=0,得x=0,或y=0当x=0时,代入方程1:-y^2+根号y^2=a,即y^2-|y|+a=0,解得|y|=[1±√(1-4a)]/2当y=0时,代入方程1:x^2+根号x^2=a,即x^2
∵|x|=3,∴x=±3;∵y2=16,∴y=±4;∵|x+y|=1,∴x+y=±1;∴x=3,y=-4或x=-3,y=4.∴xy=-12;∴A=4x2-2xy+4y2=4(x+y)2-10xy=4+
10拆成1+9X2-2X+1+Y2-6Y+9=0(X-1)2+(Y-3)2=0平方大于等于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-3=0X=1,Y=
x²-2x+y²+6y+10=0,变换得(x-1)²+(y+3)²=0,∴x=1,y=-3∴(x2-2xy)/(xy+y2)=(1²-2*(-3))/
条件变换:(x-3)^2+(y+1)^2=0即:y+1=0x-3=0所以:立方根号x2-y2=2
(1)2A-B=2(3x2+3y2-5xy)-(2xy-3y2+4x2)=6x2+6y2-10xy-2xy+3y2-4x2=2x2+9y2-12xy;(2)当x=3,y=−13时,2A-B=2x2+9
x^2+xy+y^2=2≥3xyxy≤2/3-2xy≥-4/3,x^2-xy+y^2=x^2+xy+y^2-2xy=2-2xy≥2/3当且仅当x=y时取等号再问:>=2/3且
(3A-2B)-(2A+B)=3A-2B-2A-B=A-3B,将A、B代入,即得:4x2-4xy+y2-3(x2+xy-5y2)=4x2-4xy+y2-3x2-3xy+15y2=x2-7xy+16y2
∵4x2+8xy+9y2=4x2+2xy+9y2+6xy=2(2x2+xy)+3(3y2+2xy),2x2+xy=6,3y2+2xy=9,∴2(2x2+xy)+3(3y2+2xy)=2×6+3×9=3
因为x²+4y²+x²y²-6xy+1=0(x²-4xy+4y²)+(x²y²-2xy+1)=0(x-2y)²