解方程组x:y=5:3
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3x+2y=21①2x-5y=-11②①*2得6x+4y=42③②*3得6x-15y=-33④③-④得19y=42+3319y=75y=75/19代入①得3x+2*75/19=213x=21-150/
将y=2x-5代入x+3y=-1得到x+3(2x-5)=-17x-15=-1x=2代入y=2x-5,y=2*2-5=-1
5x+y=369y-x=2即45y-10+y=36y=1x=7
【参考答案】1、3x+5y=8①2x-3y=-1②①x2得6x+10y=16③②x3得6x-9y=-3④③-④得19y=19即y=1把y=1带入②得x=1∴原方程组的解是x=1,y=12、x+y=9①
补充题目:已知方程组5x+y=3;ax+5y=4与方程组x-2y=5,5x+by=4有相同的解,求a,b的值.解答;说明,最后相同的解是四个方程的解也为方程组5x+y=3,x-2y=5的解此方程组的解
{5(x+y)+3(x-y)=2{7(x+y)-3(x-y)=-6原方程组化简得﹛4x+y=1(1)2x+5y=-3(2)(1)×5得20x+5y=5(3)(3)-(2)得18x=8x=4/9代入(1
(x+y)/2+(x-y)/3=6①5(x+y)-2(x-y)=4②由①得3x+3y+2x-2y=365x+y=36y=36-5x③由②得5x+5y-2x+2y=43x+7y=4④③代入④得3x+25
5(x+y)+3(x-y)=908x+2y=901式5(x+y)-3(x-y)=302x+8y=302式1式乘以4-2式解得x=11y=1
设a=x+y,b=x-y原方程组为:a/2+b/3=6,即3a+2b=36,即:12a+8b=1444a-5b=12,即:12a-15b=36相减得:23b=108,得:b=108/23,再得:a=1
方程化为-x+7y=1117x+3y=272将1式化为x=7y-113则将3式代入2式可得7(7y-11)+3y=2752y=104y=2x=7×2-11x=3所以解得x=3y=2
{(x-2)(y+3)=(x+1)(y-1){(x+1)(y+1)=(x-1)(y+5){xy+3x-2y-6=xy-x+y-1{xy+x+y+1=xy+5x-y-5{4x-3y=5(1){4x-2y
先将第一个等式整理得12X+Y=36,第二个等式整理得-X+9Y=2,由第一个等式得Y=36-12X,通过换元法得-X+9(36-12X)=2,解出X=322/109,再把X=322/109代入-X+
8x+3y+2=0①6x+5y+7=0②①×5得40x+15y+10=0②×3得18x+15y+21=0两式相减:22x-11=0解得x=1/2代入①得4+3y+2=0解得y=-2所以方程组的解为x=
令x/4=y/5=K,则x=4k,y=5k.所以12k-10k=10.解得K=5.则x=4k=20,y=5k=25.所以x=20,y=25
化简得:-x+7y=11①7x+3y=27②①式×7得:-7x+49y=77③②+③得:52y=104∴y=2代入①得:x=3∴x=3,y=2
1)1/2x-2y=-74,①x-6y=-12②2①-②得2y=136y=68代入①得x=4202)x/5-y/2=2,化简2x-5y=20①2x+3y=4②①-②得-8y=16y=-2代入①得2x=
解将x+y=3代入1/2(x+y)-3y=5∴1/2×3-3y=5∴3y=3/2-5∴3y=-7/2∴y=-7/6∴x=25/6
展开x^2-2y^2-xy=-5x^2-2y^2+xy=7所以x^2-2y^2=1xy=6上式除以下式,解分式方程x/y=3/2或-4/3(舍去)所以x^2=9y^2=4x=3y=2或x=-3y=-2
可能是0<X0=X0≤X≤1X>1当0<X时,|X+Y|=1原式=Y-X=1Y=1+X|X|+2|Y|=3变2(1+X)-X=3X=1所以Y=0当0=X时Y无解,不成立.当0≤X≤1时X+Y=1X+2