若x^2-3y-5=0

3x=4Y.X/Y=4/3,x-y)/y=(X/Y)-1=1/3,（3x+2y)/(2x+3y)=(4Y+2y)/(8/3y+3y)=18/17（因为3x=4Y,2x=8/3y）再问：若3X-4Y=0

/>（x+y+3）(x-y-2)=0x,y互为相反数则x+y=0...(1)带入上式3（x-y-2）=0x-y=2...(2)联立（1）（2）得x=1,y=-1

2x-y-3=3x+2y+1=0,x=5/7,y=-11/7

x²+y²-4x-2y+5=0x²-4x+4+y²-2y+1=0(x-2)²+(y-1)²=0x-2=0x=2y-1=0y=1(x+y)/2

(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^5+x^4y+x^4+x+y+1=0x^4(x+y+1)+x+y+1=0(x^4+1)(x+y+1)=0然后因为x^4+1不可能等于0所以只有x+y+1=0x+y+1=03x+2y=1这两个公式,

∵|2x-y+5|+(x+2y-4)的平方=0∴2x-y+5=0,x+2y-4=0∴2x-y=-5,x+2y=4x-3y=-9则（2x-y)的三次方-（x-3y)(y-2x)的平方=(-5)^3-(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

3x+4y=x+2y+62x-x+4y-2y=62x+2y=6x+y=6/2x+y=3

√x(√x+√y)=3√y（√x+5√y）x+√xy=3√xy+15yx-2√xy-15y=0(√x+3√y)(√x-5√y)=0∵√x+3√y>0∴√x=5√yt=x/y=25(2x+2√xy+3y

题目设置挺好的不会很变态,没什么难度由4x-3y-6z=0,x+2y-7z=0,可以解得x=3z,y=2z,将它代入代数式5x*5x+2y*2y-z*z/2x*2x-3y*3y-10z*10z=（25

3x-5y=0,则x+y/x=（8/5）,x-y/y=（2/3）,2x-3y/2x+3y=(1/19)因为3x-5y=0所以3x=5y设x=5,y=3,可以解得3x-5y=0,则x+y/x=（8/5）

若x-y/x+y=5则x-y=5(x+y)所以求x-y/2x+2y+5x+5y/3x-3y=5(x+y)/[2(x+y)]+5(x+y)/3(x-y)=5/2+5(x+y)/[3*5(x+y)]=5/

x=-2.5y=-3再问：过程再答：2x+y/3-2y=0①2(2x+y)-5=7y②展开②式，4x+2y-5=7y，移项整理的得4x-5y=5③将①整理得2x-5y/3=0④将④×2得4x-10y/

天啊,小朋友很简单因为x,y相反数,所以,2x,2y就抵消了,3x/y呢,就变成了-3,5-3=2,所以等于2

16当x=4,y=1时3x+4y=3*4+4*1=12+4=16再问：…………为什么是“当x=4,y=1时”，线性规划么？再答：∵x+2y-5=02x+y-7=0的交点坐标是（3，1）∴可取的坐标是（

设|5x-2y-3|=a,x+6y-11=b,则由题得,a+b*b=0且啊a>0.b*b>0,所以,a=0,b=0所以得5x-2y-3=0x+6y-11=0联立求解为x=5/4,y=13/8

x（x*x-1)+x(5-x*x)-6y+7=-x+5x-6y+7=2(2x-3y)+7=2*(-4)+7=-8+7=-1再问：能在写详一点吗-x+5x-6y+7再答：x（x*x-1)+x(5-x*x

有题意得x+y-3>=0xy+x+y-2>=0因为根号x+y-3+绝对值xy+x+y-2=0则x+y-3=0xy+x+y-2=0xy=-1x+y=3x^2+y^2=11x/y+y/x=(x^2+y^2

2x-3y=02x=3yx=1.5y5x+4y/3x-2y=7.5y+4y/4.5y-2y=11.5y/2.5y=4.6