∵2x 2 +3y-7=8，∴2x 2 +3y=15．4x

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 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= 已知2x+2y=-8,4x+y=15求（x-y)^-(3x+2y)^ 9y=3x-(x-1),4(x+y)-(2x+4)=8y x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20 4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 (x+y)(x+2y)(x+3y)(x+4y)=-40 计算(x^8-x^7y+x^5y^3-x^4y^4+x^3y^5-x^y^7+y^8)(x^2+xy+y^2)