9x^2-y^2-4y-4=

4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= (x-4y)(2x+y)= 常微分方程的通解dy/dx=(x-y+1)/(x+y-3)y^4=2y^n+y=0y''+6y'+9y=e^(-3x)y''+y'-2y=4e^(2x) 已知X.x+y.y-4x+2y+5=0,求4X.X-12X Y+9Y.y的值 根据3（x+y)-2(x-y)=11,4(x+y)+3(x-y)=9可得出x+y= ,x-y= y'=（y/x）^2+y/x+4微分方程 2x-y=2,求[(x²+y²)-(x-y)²+2y(x-y)]÷4y 9y=3x-(x-1),4(x+y)-(2x+4)=8y [(x+y)(x-y)-(x-y)²+2y(x-y)]÷4y 4x方y/(x-2y)(x+2y)怎么算[x方/x-2y]-4x方y/(x-2y)(x+2y)=? (x+y)^2(x-y)^2(x^4+x^2y^2+y^4)=? 81/8*(-x-y)^6*(x-y)^3*4/9(x+y)^4*(y-x)^2 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 （x+y）/2- x-y/2=6 3(x+y)=4(x-y) x+y/3+x-y/2=6 4(x+y)-2(x-y)=40