x的平方加y的平方等于10,求代数式x加y乘以x减去y加上2y的平方的值-搜答案-智慧作业帮

应该是x^2-2x+y^2+6y+10=0配方：x^2-2x+1+y^2+6y+9=0(x-1)^2+(y+3)^2=0得x=1y=-3所以x+y=-2

x^2-2x+y^2+6y+10=0(x-1)^2+(y+3)^2=0(x-1)^2=0x-1=0x=1(y+3)^2=0y+3=0y=-3x+y=1-3=-2

x=4.6415888336127788924100763509194y=10-x=10-4.6415888336127788924100763509194=5.3584111663872211075

X²+Y²=10..(1)X+Y=6..(2)(2)²-(1)得2XY=26XY=13如果认为讲解不够清楚,

x^2+2x+y^2-6y+10=0=(x^2+2x+1)+(y^2-6y+9)=0=(x+1)^2+(y^2-6y+3^2)=0=(x+1)^2+(y-3)^2=0x=-1y=3xy=-3

x^2-2x+y^2+6y+10=0x^2-2x+1+y^2+6y+9=0(x-1)^2+(y+3)^2=0x-1=0,y+3=0x=1,y=-3(x-y)/(x+y)=4/(-2)=-2

x^2+y^2=6y-4x-13x^2+4x+4+y^2-6y+9=0(x+2)^2+(y-3)^2=0x=-2y=3x^2-y^2=(-2)^2-3^2=4-9=-5

看看能理解吗

(x+y)²=20,∴x²+y²+2xy=20(x-y)²=40,∴x²+y²-2xy=40两个式子相交得2（x²+y²

x²+y²-8x-10y+41=0(x²-8x+16)+(y²-10y+25)=0(x-4)²+(y-5)²=0平方大于等于0,相加等于0,

两式相消去y,得：z^2-x^2=3,即：（z+x）*（z-x）=3.因为：xyz为正整数所以：z+x为正那么z-x也为正.同时z+x>z-x,且z+x为正整数,z-x也为正整数.3=1*3所以：z+

解题思路：此题主要考查了完全平方公式的应用；解答时整体求解xy解题过程：解：∵x+y=6∴(x+y)2=36即：x2+2xy+y2=36∵x2+y2=12∴12+2xy=3

3∵x/y=1/2∴y=2x故（x^2+2xy+y^2)/(x^2-xy+y^2)=(x+y)^2/(x^2-xy+y^2)=(x+2x)^2/(x^2-x·2x+4x^2)=9x^2/(3x^2)=

xy=0.5×【（x-y）-x-y】=1-9=-8

（x+y）平方=x平方+2xy+y平方=13（x-y）平方=x平方-2xy+y平方=9两式相加得2（x平方+y平方）=22,x平方+y平方=11两式相减得4xy=4,xy=1

x+y=a-----得到(x+y)²=x²+2xy+y²=a²①x-y=b-----得到(x-y)²=x²-2xy+y²=b