y＝3x-5 y＝x-1分之x-2 y＝根号x-1-搜答案-大师作文网

10/(x+y)+3/(x-y)=-5.(1)15/(x+y)-2/(x-y)=-1.(2)(1)×3-(2)×2得：(9+4)/(x-y)=-13x-y=-1.(4)(1)×2+(2)×3得：(20

1/x+1/y=2(x+y)/xy=2x+y=2xy(2x-xy+2y)/(3x+5xy+3y)=[2(x+y)-xy]/[3(x+y)+5xy]=(4xy-xy)/(6xy+5xy)=3xy/11x

答除了5x+2=y其他的2分之1x=y2x=3分之2y0.5分之y=3分之x7分之x=3分之y0.7y=x他们成正比例原因他们都满足y=kx（k≠0）的形式,两个量满足y=kx（k≠0）的形式,则两个

用换元法,设x+y=s,x-y=t,则原方程组为,s/2+t/3=6,①4s-5t=2,②将①×15+②,得,23s/2=92解得s=8,t=6即x+y=8,x-y=6两式加,得,x=7,y=1所以方

（x+y）/2+(x-y)/3=6①4(x+y)-5(x-y)=2②①*8得4(x+y)+8/3(x-y)=48③③-②得（8/3+5）(x-y)=46解得x-y=6④把x-y=6带入②解得x+y=8

即5(x+y)+3(x-y)=90,5(x+y)-3(x-y)=-30所以x+y=6,x-y=20因此x=13,y=-7

3:5啊

2（x+2y）＝x²+y²+5整理得(x-1)^2+(y-2)^2=0x=1,y=2(x²+y²)/(3x-4y)=-1

反比例

x=三分之五y代入x+y分之x-y消去y得：四分之一

（2x+(y-1)）(2x-(y-1))=4x^2-(y-1)^2(3x+y)(3x-y)=9x^2-y^2相减得4x^2-y^2+2y-1-9x^2+y^2=-5x^2+2y-1带入得-5*1/25

3x/4+2y=(2x+y)/5=(x-y+1)/6则3x/4+2y=(2x+y)/5―→15x+40y=8x+4y→7x+36y=0――①(2x+y)/5=(x-y+1)/6―→12x+6y再问：麻

13y-4x

因为：3分之x+1=4分之y+3=5分之x+y,所以：（x+1）/3=（y+3）/4=(x+y)/54x+4=3y+94x=3y+55x+5=3x+3y2x=3y-5x=5y=5则x+2y+3分之3x

x-4y分之3x+4y-x分之x+y-x-4y分之7y=3x/(x-4y)-(x+y)/(x-4y)-7y/(x-4y)=(3x-x-y-7y)/(x-4y)=(2x-8y)/(x-4y)=2

原式=5x根号(xy)/3根号(y/x)*1/3根号(x/y)=5/9*根号(xy*x/y*x/y)=5x/9y根号(xy)

4分之x－y＝﹣1(1)x＋4y＝4,(2)（2）-(1)×4得：8y=8y=1代入(2)得：x=0所以：x=0；y=10.2x＋0.5y＝5分之1(1)0.4x＋0.1y＝5分之2(2)(1)×2-

原式等价于10(x+1)=5(y+3)=4(x+y)10(x+1)=5(y+3)可得2x-y=15(y+3)=4(x+y)可得4x-y=15解得x=7y=13x+2y+3=363x+2y+1=48两式

y＝(x^2-4x+3)/(2x^2-x-1)=(x-1)(x-3)/[(2x+1)(x-1)]=(x-3)/(2x+1)(x≠1)=1/2-7/[2(2x+1)]值域=(-∞,-2/3)U(-2/3