12x+9y=81
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|x-y|=(x−y)2=(x+y)2−4xy.故答案为-4xy.
当x>0,y>0时,方程组整理得:2x+y=10x=12,解得:x=12,y=-14,不合题意;当x>0,y<0时,方程组整理得:2x+y=10x−2y=12,解得:x=6.4,y=-2.8;当x<0
由题意得x+y=5mx−y=9m2x−3y=9,解得x=7my=−2m,代入方程2x-3y=9,解得m=920.故本题答案为:920.
(1)由已知得:x-y=-5,∴9m=-5,∴m=-59,(2)已知方程3x+2y=17与方程组的解相同,所以得:三元一次方程组x+2y=3mx−y=9m3x+2y=17,解得:m=1.
(x+2y)(2x+y)-(3x-y)(x+2y)=(2x^2+5xy+2y^2)-(3x^2+5xy-2y^2)=4y^2-x^2=1-81=-80
4-12(x-y)+9(x+y)^2=[3(x+y)]^2-12xy+2^2=[3(x+y)-2]^2=(3x+3y-2)^2
9(x-y)^2+12(x^2-y^2)+4(x+y)^2=[3(x-y)]^2+2*3(x-y)*2(x+y)+[2(x+y)]^2=[3(x-y)+2(x+y)]^2=(5x-y)^2
[(x+y)2-(x+y)(x+3y)-4y2]÷2y,=[x2+2xy+y2-x2-3xy-xy-3y2-4y2]÷2y=(-2xy-6y2)÷2y=-x-3y,当x=-2,y=12时,原式=-(-
原式=(x-y)[(x-y)^2-6(x-y)+9]=(x-y)(x-y-3)^2很高兴为您解答,祝你学习进步!不懂可追问!
∵x²+y²-4x+2y+5=0x²-4x+4+y²+2y+1=0(x-2)²+(y+1)²=0x-2=0y+1=0∴x=2y=-14x
4-12(x-y)+9(x-y)²=[2-3﹙x-y﹚]²=﹙2-3x+3y﹚²再问:那个小的2是怎么弄的再答:二次方,就是平方
方法一:(1)×2-(2)得:3y=3,y=1.将y=1代入(1)得:x+2=6,x=4.∴x+y=1+4=5x+y=5.方法二:两个方程相加,得3x+3y=15,x+y=5.
这是完全平方原式=[3(x-y)]²+2×[3(x-y)]×2+2²=[3(x-y)+2]²=(3x-3y+2)²
①+②×3得,-x=-3,解得x=3,把x=3代入②得,-4×3+3y=-5,解得y=73.故原方程组的解为x=3y=73.
不妨方程x-2y=-9标注为(1),方程3x-y+z=4标注为(2),方程y-z=3标注为(3),则有(2)-(1)*3=(3x-y+z)-(x-2y)*3=4-(-9)x3,即为5y+z=31,标注
12x^2yz-9x^2y^2-x^2+xy-xzp(x-y)+q(y-x)=3x^2y·(4z)-3x^2y·(3y)=-x·x+(-x·-y)+(-x·z)=p(x-y)-q(x-y)=3x^2y
x(x+y)(x-y)-x(x+y)2=x(x+y)[(x-y)-(x+y)]=-2xy(x+y).当x+y=1,xy=-12时,原式=-2×(-12)×1=1.
3y=2x,两边同时乘以1/3x可得y/x=2/3;y/3=x/2,两边同时乘以3/x可得y/x=3/2;12/x=9y,两边都乘以x/9可得x/y=4/3.