2x-5y=16 kx 4y=9这个方程组怎么解-搜答案-搜搜考试网

x*x+4y*y+2x*x-4y+2=0应该是x*x+4y*y+2x-4y+2=0可变换为（x+1)^2+(2y-1)^2=0x=-1,y=1/2,剩下的自己做一下,关键是上面一步要会

设x-y=mx+y=n则6m-2n=143m+n=5解得m=2n=-1即x-y=2x+y=-1解得x=1/2y=-3/2

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

再问：其他呢？再答：等等。这个是方法，要不要自己尝试下？

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再问：亲，是代入法哦！再答：代入法①式得3x+3y-4x+

∵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&#

x-y / 5y= (y-x)^2 / ( )

x-y/5y=(x-y)(x-y)/(5y(x-y))=(y-x)^2/(5y(x-y))

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

x=66/37y=-28/37

解(x-y)(x+y)-(x-2y)²+x(3x-5y)-(x-y)(x-2y)=(x²-y²)-(x²-4xy+4y²)+(3x²-5xy

5x=3y,x=3y/5(2x+y)的平方=5x(x+y)+94x²+4xy+y²=5x²+5xy+9x²+xy-y²+9=09y²/25+

4x=9yx=9/4*y(1)(x+y)/y=[(9/4)y+y]/y=(9/4+1)y/y=9/4+1=13/4(2)(y-x)/2x=[y-(9/4)y]/[2*(9/4)y]=(1-9/4)y/

(3x-5y-11)*(3x-5y-11)=(3x-5y-11)平方所以原式=（3x-5y-11)平方+|9x+2y-16|=0因为平方的数大于等于0绝对值的数也大于等于0所以3x-5y-11=0、9

X+2y=o3X+4y=6x=6,y=-35X+6y=167X-9Y=5x=2,y=1再问：还要详细的步骤帮帮忙再答：

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

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

9(x+2y)的2次方-25(x-2y)的2次方=[3(x+2y)+5(x-2y)][3(x+2y)-5(x-2y)]=(3x+6y+5x-10y)(3x+6y-5x+10y)=(8x-4y)(16y