5y-9x=-2 3x 4y=29
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3x+2=y和11x=y,得到x=1/4,y=11/4,5X+4=Y和7X+6=Y,得到X=-1,Y=-1代入9X+8=y,不成立,方程组无解..
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多项式2x3y2-3x2y3-5x4y+6xy4-5中,x的系数依次3,2,4,1,按x的降幂排列是-5x4y+2x3y2-3x2y3+6xy4-5.
y-x=3(1)7x+5y=-9(2)(1)*7+(2)12y=12y=1x=-2
解13x-2y=9x-3y=2将式2左右两边同时乘以3得3x-9y=6与式1相减有-9y+2y=6-9解得y=3/7代入代2有x-3*3/7=2解得x=23/7故x=23/7y=3/7解2x+y=5x
将11x=y即y=11x分别代入前面四个方程式,1、方程式一得3x+2=11x,x=1/4,则y=11/4;2、方程式二得5x+4=11x,x=2/3,则y=22/3;3、方程式二得7x+6=11x,
X=2,Y=3或X=3,Y=2
∵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
因为(x-y)/(x+y)=3,则(x+y)/(x-y)=1/3则5(x-y)(x+y)-(x+y)/2(x-y)=5*3-1/(3*2)=15-1/6=89/6
2/(x+y)+5/(x-y)=189/(x+y)-10/(y-x)=66设x+y=a,x-y=b,原方程化为2/a+5/b=18-----1(1)9/a+10/b=66-------(2)(2)-(
x:y=2:3和5x+3y=38y=3x/2;5x+3y=385x+9x/2=3819x=76x=4y=63y+x/y=8和9y-2x/y=96y+2x/y=16;9y-2x/y=915y=25y=5
另a=1/(x+y),b=1/(x-y);则2a+5b=18;9a+10b=66;解得a=6,b=6/5;即 &nbs
3x+2y=13①3x-2y=5②由①+②,得6x=18,x=3x=3代入②,得y=2该方程组的解集为x=3,y=2x-y/3=x+y/2+1①2x-5y=9②由①,得-y/3=y/2+1,y=-6/
解(x-y)(x+y)-(x-2y)²+x(3x-5y)-(x-y)(x-2y)=(x²-y²)-(x²-4xy+4y²)+(3x²-5xy
②*39x+12y=87③③+①17y=102y=6把y=6代入②x=5/3∴x=5/3y=6
5x=3y,x=3y/5(2x+y)的平方=5x(x+y)+94x²+4xy+y²=5x²+5xy+9x²+xy-y²+9=09y²/25+
y=x+3代入7x+5y=9得7x+5x+15=9x=-0.5代入y=x+3得y=2.5∴﹛x=-0.5,y=2.5是原方程组的解再问:{3x+4y=16,5x-6y=33再答:{3x+4y=16(1
3X-3Y=93(X-Y)=9X-Y=3.①X+Y=5...②∴①+②得:2X=8X=4∴X=4Y=1请及时点击【采纳为最佳回答】按钮~再问:代入法这方法我们也没教过再答:X=5-Y带入3x-3y=9
x=25y=15
x+y=3则y=3-x带入x+2y=9解得x=-3,y=6剩下的都这样解