9x^2-y^2-6y-4

81/8*(-x-y)^6*(x-y)^3*4/9(x+y)^4*(y-x)^2 (x+y)^2+6(x+y)+9 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) 【2(x-y)(x-y)(x-y)-8(x-y)(x-y)(x+y)+6y(x-y)(x-y)]/2(x-y)(x-y) (66x^6y^3-24x^4y^2+9x^2y)÷(-3x^2y)化简 (x-2y)^2-6(2y-x)(x+y)+9(x+y)^2因式分解 解二元一次方程 {3(x+y)-4(x-y)=-9 x+y/2+x-y/6=1 4x-y/2根号x+根号y 9x-6根号xy+y/3根号x-根号y 因式分解 （1）.(x+y)(x+y-6)+9 （2）.x²-16y²-x-4y 计算(x-y)^7÷(y-x)^6+9-x-y)^3÷(x+y)^2 9(x+y)-2(x+y)-6(x+y)+18(x+y)合并同类项 合并同类项：9(x+y)-2(x+y)-6(x+y)+18(x+y) 4x-3y/x-2y÷6y-8x/y-2x （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 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 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