2x-5y=-21x 4x 3y=23-搜答案-搜狗做题网

原式=(9x²+24xy+16y²-4x²+y²-5x²+6xy-y²)÷(-2y)=(30xy+16y²)÷(-2y)=-15x

(4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=4x-2y-z-5x[6y-(x+y)]+x-(3y-10z)=4x-2y-z-30xy+5x²+5xy+x-3

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

｛2x-5y=21①,{2x+y=6②①+②-6y=15,y=-5／2,把y=-5／2②得：2x=6+5／2x=17／2｛x=17／2,y=-5／2｝∴原方程组的解为：{x-3y=1①{y=-2x+3

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

5(x+y-2)=3-y

x=5y=-2

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+

楼上的全错,{(3x+y)(3x-y)-(x-5y)(5x-y)-(x-2y)²}÷(-4x)={9X²-(5x²-xy-25x²+5y²)-(x&s

(x*x+y*y)(x*x+y*y)-4x*x*y*y=(x^4-2x^2y^2+y^4)=(x^2-y^2)^2=0x^2=y^2x/y=±1(x*x+5xy+y*y)/(x*x+2xy+y*y)=

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

X^2表示平方X^2+4X+4+Y^2-2Y+1=0(X+2)^2+(Y-1)^2=0因为平方大于=0所以X+2=0Y-1=0X=-2Y=1X^2+Y^2=5

你要问什么呢?请说的明白点再问：过程。答案

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+

再答：再答：看后面这个图再答：不懂可以问我

1,-3再问：过程。。。再答：★（x²－2x)+（y²－4y）=5★（x－1）²+（y－2）²=1+4－5★（x－l）²=0,（y－2）²=

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

原式=x-x+x-x+……-x+(2-1+4-3+5-4+……+2008-2007-2009）y=0+(1×1004-2009)y=-1005y=1005/2