X:y=3,则分式(x-y)的平方 x的平方-y的平方-搜答案-智慧作业帮

1/x+1/y=3∴x+y=3xy3x-2xy+3y/x+xy+y=[3(x+y)-2xy]/[(x+y)+xy]=(9xy-2xy)/(3xy+xy)=7/4

代入方法：分母：3x-3xy+3y=3(x+y)-3xy=3•(3xy)-3xy=9xy-3xy=6xy分子：x+xy+y=x+y+xy=3xy+xy=4xy所以原式=6xy/4xy=3/

已知1/x-1/y=3,应该是1/x+1/y=3,[按原式得不出结果!]如此,则3xy＝x+y（3x-xy+3y）/（x+xy+y）＝2

4y-3x=0得4y=3x得y=0.75x∴y/(x+y)=0.75x/(x+0.75x)=0.75x/1.75x=3/7

x/x-y=a取倒数(x-y)/x=1/a1-(y/x)=1/a(2x^2y-2xy^2)/3x^2y上下同时除以x²y=(2-2(y/x))/3=(2/3)(1-(y/x))=(2/3)(

=-(x+y)-3/5=-5-3/5=-5.6

x/2=y/3x=2y/3(3x+2y)/(2x-3y)=[3(2y/3)+2y]/[2(2y/3)-3y]=4y/(-5y/3)=-12/5

扩大后分式的值等于2530x÷(50x+70y)=3x÷（5x+7y）=25

因为已知x/y=2,所以x=2y代入算式得：（4y*y-2y*y+3y*y）/(4y*y+2y*y+6y*y)化简原式=5/12

4y-3x=0,则4y=3x,即x:y=4:3(x+y):y=x:y+y:y=4:3+1=7:3即2又三分之一.

(10x-11y)/(x-y)=[(8x-8y)+(2x-3y)]/(x-y)=8+(2x-3y)]/(x-y)=8+0=8

(x+y)/z=(x+z)/y=(z+y)/xx,y,z等价x=y=z(x+y)(x+z)(z+x)/xyz=8

1x=4y代入

=[(8x-8y)+(2x-3y)]/(x-y)=[(8x-8y)+0]/(x-y)=(8x-8y)/x-y=8(x-y)/x-y(这是乘法分配律)=8(约分同时除以x-y)

3x-2y/2x-3y=[3(x/y)-2]/[2(x/y)-3]分子分母同时除以y=(4-2)/(8/3-3)=2/(-1/3)=-6

1/x-1/y=5即,(y-x)/xy=5即,x-y=-5xy(3x-2xy-3y)/(x+xy-y)=[3(x-y)-2xy]/[(x-y)+xy]=(-15xy-2xy)/(-5xy+xy)=(-

C

y=4x带入3x-y=3x-4x=-xx+y=x+4x=5x(x+y)/(3x-y)=5x/(-x)=-5

x2+4x+4+y2-6y+9=0(x+2)2+(y-3)2=0∵(x+2)2≥0,(y-3)2≥0∴要使方程成立,必须x+2=0,y-3=0即x=-2,y=3自己代入吧!后面看不太懂,是打错了吗?哪

1/x-1/y=2010等式两边同乘xy得y-x=2010xy即x-y=-2010xy,代入分式中,原式=（-2010xy+2xy)/(-2010xy)=1004/1005