求分式2y-xy分之x的平方-2x的值,其中x=-6,y=28-搜答案-灵鹊做题网

2/xy=2(y-x)/xy(y-x)3y/(xy-x^2)=3y^2/xy(y-x)如果不懂,请追问,祝学习愉快!

x平方）+（y平方）-4x-6y+13+0可化为（x-2）^2+(y-3)^2=0x=2,y=3代入原式=（9-4）/6=5/6

x-3y=0且xy≠0,所以x=3y(x≠0,y≠0)带入分式,(9y-3y+y)/(9y+3y+y)=7/13

x+2y=0x=-2y分式2x的平方+xy+y的平方分之x的平方+2xy-y的平方=(x²+2xy-y²)/(2x²+xy+y²)原式=(4y²-4y

x-y=x/y两边同乘以y得xy-y^2=x移项xy-x=y^2即x(y-1)=y^2x=y^2/(y-1)

x/y=3=>x=3y原式=(9y²+2*3y*y-3y²)/(9y²-3y*y+y²)=12/7再问：能不能先化简，后代入？再答：可以是可以，x²+

x平方减y平方等于0,(x+y)(x-y)=0x+y=0或x-y=0当x+y=0,则x=-y3x平方减2xy加4y分之x平方减3xy加5y平方=(3y²+2y²+4y²)

这个不能约分,已经是最简了不能化简

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(4-x²)/(x²y-2xy)=-(x²-4)/(x²y-2xy)=-(x+2)(x-2)/xy(x-2)=-(x+2)/xy愿对你有所帮助!

∵x/y=2/3∴设x=2t,y=3t∴(x²+3xy)/(x²+xy-6y²)=(4t²+3×2t×3t)/(4t²+2t×3t-6×9t²

(x+3y)/(x²+xy)+(y-x)/(xy+y²)=(x+3y)[x(x+y)]-(x-y)/[y(x+y)]=[(x+3y)y-x(x-y)]/[xy(x+y)]=(xy+

因为x=3y,所以原式=[（3y)²-3y·y+y²]分之[(3y)²+2·3y·y-3y²]=7y²分之12y²=7分之12

x的平方+2xy+y的平方分之x的平方-y的平方=(x+y)(x-y)/(x+y)²=(x-y)/(x+y)∵x+y=2,x-y=1∴原式=1/2

x²-3xy+2y²=(x-y)(x-2y)=0x-y≠0,所以x-2y=0x=2y原式=(4y-3y)/(2y-y)=y/y=1

y-x=3xyx-y=-3xyx-2xy-y=-5xy2x+3xy-2y=2(x+y)+3xy=-6xy+3xy=-3xy分式x-2xy-y分之2x+3xy-2y=5/3

xy/(x²-y²)=xy/(x+y)(x-y)=x*(-2x)/(x-2x)(x+2x)=-2x²/(-3x²)=2/3

方法一：取特殊值x=1,y=2,代入即可.方法二：由y/x=2,得y=2x,代入要求的式子也行,但是注意运算要小心点.

(2x^2+3xy-2y^2)/(x^2+3xy+2y^2)={(2x-y)(x+2y)}/{(x+y)(x+2y)}=(2x-y)/(x+y)=02x-y=0

x/y=2则x=2y代入下式(x^2+y^2)/xy=（4y^2+y^2）/(2y^2)=5/2