{X-Y=630 {X(1+20%)+Y(1-10%)=(X+Y)(1+12%) 怎么解

解方程组:(x+3)(y-2)=(x-3)(y+10),(x+1)(y+3)=(x-2)(y+12) 用加减法解方程组:{(x+y)/6+(x-y)/10=3 (x+y)/6+(y-x)/10=-1 解方程组x+y/6+x-y/10=3,x+y/6+y-x/10=-1 先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y x-y=2y 0.2x+3y=1 这个二元一次方程怎么解? 微分方程 (x^2)*y"-x*y'+y=1怎么解呢? y'=(x+y+1)^2-(x+y)这个一阶微分方程怎么解啊? y=[x-1], 1.已知1/x+1/y=-1/x+y,则y/x+x/y=? {3(x+y)+3(y+x)=1,3(x+y)+4(y-x)=-1 ｛4/(x+y)+6/(x-y)=3 ｛9/(x-y)-1/(x+y)=1 (3x-y)^2+(3x+y)(3x-y),x=1,y=-2