x=8+2y-y^2x=0,y=-1,y=3所圍

已知2x-y=0,求分式【1+（3*y*y*y/x*x*x-y*y*y）】/【1+（2y/x-y）】的值注：x*x*x-y*y*y=（x-y）*（x*x+xy+y*y）这个题lz想太复杂了,y=2x代进去,原式=(1+(24x^3/x^3-

x-y/x-x+y/y-(x+y)(x-y)/y²y/x=2以上错误,修改如下：y/x=2→y=2x(x-y)/x-(x+y)/y-(x+y)(x-y)/y^2=((xy-y^2)-(x^2+xy))/xy-(x^2-y^2)/y

【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2=很累-3x-2y

12y(x-y)^2-8(x-y)^3=?12y(x-y)²-8(x-y)³=4(x-y)²[3y-2(x-y)]=4(x-y)²(5y-2x)

若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值2/x-1/y=3(2y-x)/(xy)=3xy/(x-2y)=-1/3{(y/x)-[y/(x-y)]*[(x-y)/x-x+y]}/[(x-2y)/x

(3x-y)^2+(3x+y)(3x-y),x=1,y=-21041012290364原式=9x²-6xy+y²+9x²-y²=18x²-6xy=18*1²-6*1*(-2)=18

二元一次方程：2(x+y)-(x-y)=3(x+y)-2(x-y)=12(x+y)-(x-y)=32x+2y-x+y=3x+3y=3(x+y)-2(x-y)=1-x+3y=1两式相加6y=4y=2/3带入得x=3y-1=2/3x3-1=1肯

2(x+y)-3(x-y)=16(x+y)+(x-y)=512(x+y)-3(x-y)=12x+2y-3x+3y=1-x+5y=16(x+y)+(x-y)=517x+5y=618x=60x=15/2y=17/10第一个式子可化为：5y-x=

{3(x+y)-4(x-y)=4{x+y/2+x-y/6=13(x+y)-4(x-y)=4(x+y)/2+(x-y)/6=1令a=x+y,b=x-y3a-4b=4(1)a/2+b/6=1则3a+b=6(2)(2)-(1)5b=2b=2/5a

变量x,y满足约束条件,x+y>=3,x-y>=-1,2x-y-1

(x-y)^2+(x+y)(x-y)其中X=3Y=-1(x-y)^2+(x+y)(x-y)=(x-y)(x-y+x+y)=(x-y)2xx=3y=-1x-y=3+1=4原式=4×2×3=24(x-y)^2+(x+y)(x-y)=(x-y)(

(x-y)/(x+y)=3求(3x-2y-1)/(x+y-5)(x-y)/(x+y)=3求(3x-2y-1)/(x+y-5)∵（x-y)/(x+y)=3,∴可设x-y=3a.(1)(a≠0)x+y=a.(2)(1)+(2)得2x=4a,故x

(x+y)(x-y)+(x-y)平方-(x-y)(3x-y)其中x=-2y=3分之一(x+y)(x-y)+(x-y)平方-(x-y)(3x-y)=(x-y)(x+y+x-y-3x+y)=(x-y)(-x+y)=-(x-y)²=-(

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

2(x+y)3x+3y=24x+y/2xxy/2y=1{2(x+y)3x+3y=24{x+y/2xxy/2y=1的解和思路由2(X+Y)3X+3Y=24得：2(X+Y)X+Y=8①;(X+Y/2X)XY/2Y=1得：X+Y=4②;由①、②得

已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-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

y"+y'-2y=2xy"+y'-2y=2x先求y"+y'-2y=0的通r²+r-2=0,r=1或-2y=ce^x+de^(-2x)再求一个特解,设特解为y=ax+b,则y'=a,y"=0代入原式得0+a-2ax-2b=2x可求得

微分方程y"-2y'+y=x先求对应齐次方程的特征方程为r″-2r+1=0r1=r2=1齐次方程的通解为Y=e^x(C1+C2x)再求非其次方程的特特解形式为y0=e^(λx)·x^k·(Ax+B)∵P(x)=x=e^(λx)·x∴λ=0不

x+y=15x-2y=83x-y=72x-y=3x表示y和用y表示xx+y=1y=-x+1x=-y+15x-2y=8y=(5x-8)/2x=(2y+8)/53x-y=7y=3x-7x=(y+7)/32x-y=3y=2x-3x=(y+3)/2

(x+y)(2x-3y)=?（x+y）（2x-3y）=2x-3xy+2xy-3y=2x-xy-3y