{2x-3y=8{3x+7y=0.5 并且用代入法解

化简下列各式,并求值:3(x-y)²-7(x-y)+8(x-y)²+6(x-y) 其中x=2,y化简下列各式,并求值:3(x-y)²-7(x-y)+8(x-y)²+6(x-y)其中x=2,y＝5 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= 化简化简并求值 x=2 y=90(x+y)+(2x+y/2)+(3x+y/2*3)+(4x+y/3*4)+.+(8x+y/8*9)(x+y)+(2x+y/2)+(3x+y/2*3)+(4x+y/3*4)+....+(9x+y/8*9) 对不起 后面是9 ,打错了 x+y=1 5x-2y=8 3x-y=7 2x-y=3x表示y和用y表示x 已知实数x.y满足根号(x+y-8)+根号(8-x-y)=根号(3x-y-4)+根号(x-2y+7),求x,y 12y(x-y)^2-8(x-y)^3=? 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 化简并求值:2(x+y)-2/3(x-y)-3(x+y)+2/3(x-y),其中x=-2,y=1详细解答! 化简并求值“2（x+y）-2/3（x-y）-3（x+y）+2/3（x-y）,其中x=12,y-1 先化简再计算（x+y)^2-4(x+y)(x-y)+3(x-y)^2并求出x=5,y= -4/5时的值. （x+3y)²-2（x-y)（x+y)+(x+y)²其x=0.5,y=-2 2x-y=7,3x+y=8 二元一次方程组 X-Y/7-X+Y=0.5 2(X-Y)+5(X+Y)=3 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) (x+y)(x-y)+(x-y)平方-(x-y)(3x-y) 其中x=-2 y=3分之一 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= 已知x,y是有理数,并x.y满足2x^2+3y+y√2=23-3√2,x=?,y=? 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)