已知y=x-1分之6-搜答案-灵鹊做题网

1/x-1/y=2001则(x-xy-y)/(x-y)=2002/2001

∵1/x+1/y=1/6,1/y+1/z=1/9,1/z+1/x=1/15∴（1/x+1/y）+（1/y+1/z）+（1/z+1/x）=1/6+1/9+1/152（1/x+1/y+1/z）=15/90

x²+y²+6x-4y+13=0(x+3)^2+(y-2)^2=0x=-3y=2(y-1/x)/(x-1/y)=(2+1/3)/(-3-1/2)=-2/3

1/x+1/y=-2则(x-xy+y)/(x+xy+y)分子分母同除以xy=(1/x+1/y-1)/(1/x+1/y+1)=(-2-1)/(-2+1)=3

因为x:y:z=3：4：5所以设x=3k,y=4k,z=5k(k≠0)(1)z/(x+y)=5k/(3k+4k)=5k/7k=5/7(2)x+y+z=63k+4k+5k=612k=6k=1/2x=3k

由4x+y-4x-6y+10=0得(4x-4x+1)+(y-6y+9)=0(2x-1)+(y-3)=0(2x-1)=0(y-3)=0x=1/2y=3代入所求算式即可求出结果（不好意思,看不清你的所求算

x=(y-1)/(y+1)x(y+1)=y-1xy+x=y-1xy-y=-x-1y(x-1)=-(x+1)y=-(x+1)/(x-1)

用x分之3加y分之4乘以（x+y),然后化简,再用均值不等式就出来了……(3/x+4/y)乘（x+y）等于7+3y/x+4x/y然后由于x,y大于0,所以用均值不等式即可……

X+Y>=2√(XY)当X=Y时,X+Y有最小值,即X+Y=2√(XY)=2√(X²)=2XX分之1+Y分之9=11/X+9/Y=1Y+9X=XYX=Y,X+9X=X²X²

x+y=2又20分之19x-y=5分之1等式左边加左边,右边加右边.x+y+x-y=20分之632x=20分之63x=40分之63y=40分之55

ay/(y-b)

x²+4y²-6x+4y+10=0x²-6x+4y²+4y+10=0x²-6x+9+4y²+4y+1=0(x-3)²+(2y+1)

(3x-4y)÷(2x+y)=1/2所以2x+y=2(3x-4y)=6x-8y4x=9y所以x/y=9/4

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

6已知x+y=2,x-y=1,求分式x方+2xy+y方分之x方-y方的值x方+2xy+y方分之x方-y方=(x+y)(x-y)/(x+y)²=(x-y)/(x+y)=1/27已知x分之1-y

因为x＋y/2=3x＋4y/5=1,所以x＋y=2,3x＋4y=5所以解方程组得x=3,带入x＋5y＋6/3x－y＋1,得4/11

根号（Y/X）+根号（X/Y）=根号（XY）/X+根号（XY）/Y=根号(xy)*(1/x+1/y)=根号3*（x+y)/xy=根号3*（-6）/3=-2根号3

(x+y)/2-(x-y)/3=1等式两边同时乘以6,得3(x+y)-2(x-y)=63x+3y-2x+2y=6x+5y=65y=6-xy=(6-x)/5

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