x2减y2等于8 2xy等于6
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∵x2-5xy+6y2=0,∴(x-2y)(x-3y)=0∴x-2y=0,x-3y=0,即x=2y,x=3y,∴y:x等于12或13.故选C.
把z看成已知数,解3x-4y-z=02x+y-8z=0,得x=3z,y=2z原式=(9z^2+4z^2+z^2)/(6z^2+2z^2+3z^2)=14/11
∵x-y=9,xy=8,∴x2+y2=(x-y)2+2xy,=92+2×8,=81+16,=97.故选B.
A、原式=-6x2-19xy-5y2;B、原式=2x2-9xy-7y2;C、原式=x2-16xy-10y2;D、原式=8x2-13xy-15y2.故选D.
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
A=B+C=(2x2-3xy-y2)+(x2+xy+y2)=2x2-3xy-y2+x2+xy+y2=3x2-2xy.故选D.
x^2+xy-2y^2-x+7y-6=(x+2y)(x-y)-x+7y-6x+2y-3Xx-y2十字相乘得:2(x+2y)-3(x-y)=-x+7y是一次项所以原式=(x+2y-3)(x-y+2)
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=
∵x+y=2,∴12x2+xy+12y2=12(x2+2xy+y2)=12(x+y)2=12×22=2.故选A.
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))/
-3x2+6xy-3y2=-(3x2-6xy+3y2)=-3(x2-2xy+y2)=-3(x-y)2,故答案为:-3(x-y)2.
∵x2-y2=(x+y)(x-y)=6,x-y=1,∴x+y=6.故选D.
(y1z2-y2z1,z1x2-x1z2,x1y2-y1x1)再问:如何记忆?再答:线性代数与几何中讲的很明白,看看教材就行了。
6x2-xy-15y2=(2x+3y)(3x-5y)=0,所以x=-3/2y或x=5/3y
-5*2-6=-10-6=-(10+6)=-16希望我的回答对你有用,望及时采纳为满意答案.
=[x+(3-√5)/2*y][x-(3-√5)/2*y]有点牵强,但这是唯一的答案了
∵5x2-xy-6y2=0,∴(5x-6y)(x+y)=0,∴5x-6y=0,x+y=0,∴5x=6y,x=-y,∴yx=56或-1.故答案为:56或-1.
x=2,y=4!把不等式整理一下:x2(二次方)+y2/2+4-xy2y
因为x²+4y²+x²y²-6xy+1=0(x²-4xy+4y²)+(x²y²-2xy+1)=0(x-2y)²