3x-2y=5 5x 7y=91解方程
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两式相加3(x+y)-3(x-y)=46y=4xy=2/32x+2y-x+y=3x+3y=3x=3-3y=3-2=1
x+y/3+x-y/2=63(x+y)-2(x-y)=282x+2y+3x-3y=363x+3y-2x+2y=285x-y=36x+5y=285x-y=365x+25y=14026y=104y=4x=
5x+y=369y-x=2即45y-10+y=36y=1x=7
X+Y分之X-Y等于3x=-2yX+Y分之2(x-y)减X+Y分之3X+Y=(-x-3y)/(x+y)=1
4X-2Y=16P4X+7Y=7P-9Y=9PY=-P3X+7P=35X=3.5P17.5P=35P=2
.死算呗xy-2x+3y-6=xy+10x-3y-30,2x-y=4xy+3x+y+3=xy+12x-2y-24,3x-y=92式减1式,x=5,y=6
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
{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
化简x+y=105x+7y=625x+5y+2y=622y=62-50y=6x=4
{{x-y)/3-(x+y)/4=2①{(x-y)/6-(x+y)/8=3②②×2得:(x-y)/3-(x+y)/4=6③①与③矛盾∴原方程组无解
(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
2(x-y)/3-x+y/4=-1(1)6(x+y)-4(2x-y)=16(2)(1)方程两边同乘以12得8(x-y)-3(x+y)=-12合并同类项得5x-11y+12=0(3)(2)合并同类项得1
方程组整理得:2(x+y)-3(x-y)=3①4(x+y)+3(x-y)=15②①+②得x+y=3③,把③代入①,得x-y=1④,③+④得:x=2,③-④得:y=1,则原方程组的解是x=2y=1.
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+
设X+Y=A,则由a(a-3)=10得出(a-5)(a+2)=0,得a=5或a=-2.然后再分2种情况分别代入前面方程式.就能求出X、Y分别是多少了我觉得我这方法是最好解的方法了.
7x加7y还是7x减7y
∵3/x+y+2/x-y=6∴x+5y=28∵3(x+y)-2(x-y)=28∴x=5/6∴y=163/30
牛奶妹琪琪1:3x-5y=16①2x+7y=a-18②∵x,y互为相反数∴y=-x③把③代入①中,得3x-5×(-x)=163x+5x=168x=16x=2∴y=-2∴把x=2,y=-2代入②中,得2