x.y满足方程组3ax 4y=9-6ax 5y=27,那么3ax y的值是---
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根据题意得:3x+2y=4,6x-4y=33x+2y=42(3x-2y)=33x-2y=3/29x^2-4y^2=(3x-2y)(3x+2y)=(3/2)*4=6
由题得:7x+6y=2x+3y+9,x+y=3得到x=0,y=3所以m=3
x-2y=m-3①3x+y=-m②x+5y=9③①+②×2x+6x=m-3-2m7x=-m-3④②×5-③15x-x=-5m-914x=-5m-9⑤代④入⑤2(-m-3)=-5m-9-2m-6=-5m
2x+3y=k,①3x+5y=k+2②②-①,得x+2y=2③又解满足x+y=9④③-④,得y=-7所以x=16所以k=2×16+3×(-7)=11
...解那两个方程得x=11/12y=5/8则9x^2-4y^2=121/16-25/16=6
x=7,y=-2.三个方程求解,一二方程消去m,得到2x+7y=0.2x+7y=03x+2y=17二元一次方程组.
x+2y-6=0①x-y-9+3a=0②把x+y=0带入①②y-6=0y=6∴-2y+3a=9-12+3a=9a=7
由方程组{X+Y=5m,X-Y=9m解得{X=7mY=-2m∵2X+3Y=6∴14m+(-6m)=68m=6m=¾
由方程组3x+2y=a+22x+3y+9的解满足x+y=4得:[3x+2y=a+2|x+y=4[2x+3y=9将方程组合并后得:5x+5y=a+11①把①带入x+y=4中得:x+y=(a+11)/5=
x=-k,y=k代入x+9>2y得k
用加减消元法,2x-2y=1所以X-y二2分之1
x+y==5mx-y=9m相加2x=14mx=7my=5m-x=-2m所以2x+3y=14m-6m=88m=8m=1
通过上面2个式子,可以知道X-9Y=8/2a-34/3.
x-y=9a(1)x+2y=3a(2)(2)-(1)得y=-6a代入(1)得x=3a方程解满足3x+2y=17,则9a-12a=17a=-17/3方程的解为x=-17y=34
x2y+xy2=xy*(x+y)因为x+y=-(7+xy)又x+y=(9+2xy)\3所以(9+2xy)\3=-(7+xy)3+2xy\3=-7-xy5xy\3=-10解得xy=-6所以x+y=-(7
这简单个题,两个多小时没人答,不可思议.1)2x-2y=8m+2=>5y=-5m+5=>y=1-m=>x=4m+1+1-m=>x=3m+2∴x=3m+2、y=1-m2)∵x>0&y>0=>3m+2>0
x+2y=9mx-y=3m2y+y=6m3y=6my=2mx=2m+3m=5m代入2x-3y=810m-6m=84m=8m=2
三元一次方程组啊x=6my=-3m3x+2y=1712m=17m=17/12x=17/2y=-17/4
x+y=5m----(1)x-y=9m-------(2)(1)+(2),2x=14m.(1)-(2):y=-2m2x-3y=14m+6m=9,m=9/20
x-y=9m则x=y+9m,因x+2y=5m所以3y+9m=5m,则3y=-4m推出:y=-4m/3;2(x-y)=2*9m,则(x+2y)+2(X-y)=5m+2*9m,则3x=23m推出:x=23