X+1/3=3y 2(x+1)-9y=6三分之x+1=3y2(x+1)-9y=6

2(x+y)-3(x-y)=1 6(x+y)+(x-y)=51 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 解二元一次方程 {3(x+y)-4(x-y)=-9 x+y/2+x-y/6=1 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) 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 (x+y)(x-y)+(x-y)^2-(6x^2×y÷2y-2xy^2÷2y)其中x=-3,y=1/3 9y=3x-(x-1),4(x+y)-(2x+4)=8y 解二元一次方程组：3(x+y)-4(x-y)=4,x+y/2+x-y/6+1x+y/2+x-y/6+1=1 (3x-y)^2+(3x+y)(3x-y),x=1,y=-2 二元一次方程 ：2(x+y)-(x-y)=3 (x+y)-2(x-y)=1 (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 变量x,y满足约束条件,x+y>=3,x-y>=-1,2x-y (x-y)^2+(x+y)(x-y) 其中 X =3 Y=-1 化简求值:(x+y)+(2x+1/2y)+(3x+1/6y)+.+(9x+1/72y) ,其中x=1,y=-9 (7x-2y)(3x-2y-1)-(4x+3y)(9x+6y)其中x=2y=1 (x+y)+(2x+0.5y)+(3x+1/6y)+...+(9x+1/72y),当x=2,y=9时,求代数式的值 (x-2y)(x+y)-2x(-2x-3y)+6x(-x-y),其中x=-1,y=2