2x-7y=5 （1) 3x-8y=10(2)

{ x-y/7-x+y/10=1/2 {2(x-y)+5(x+y)=3 (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuai 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 x1:4x-3y=8;y=7-5x;2:2x-7y=8,3x-8y-10=0;3:4x-y=-1;4:5x-10y+15 2X+Y+Z=10,X+2Y+Z=-6,X+Y+2Z=8 5X+4Y-3Y=13,2X-3Y+7Z=19,3X-Y=2X 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) x+y=3 x+2y=9 3/x+1=y y-x=3 y=2x-3 y-3x=1 2(x+1)-y=6 7x-5y=-9 若｜y+5｜+(5x+1)^2=0,求-3(2x-y)-｛7x-[6x+2y-(10x-8y)]-x-2(3x-4y)｝ 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 7x-3y/5=5x-y/3-x+y/2 x-1/5=y+1/3 10/x+y+3/x-y=-5 15/x+y-2/x-y=-1（用换元法解此方程组） y=(x-1)(x-2)(x-3)(x-4)(x-5)(x-6)(x-7)(x-8)(x-9)(x-10)的导数在x=1