4x+8(x+y)=840 4y+9(x+y)=840

9y=3x-(x-1),4(x+y)-(2x+4)=8y ｛4/(x+y)+6/(x-y)=3 ｛9/(x-y)-1/(x+y)=1 已知4x=9y求(1)x+y/y (2)y-x/2x [(x+2y)(x-2y)-(x-2y)^2+8y(x+y)]除以4x= (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuai 已知X.x+y.y-4x+2y+5=0,求4X.X-12X Y+9Y.y的值 已知x的平方+y的平方-8x+6y+25=0,求(x-y+4xy/x-y)(x+y-4xy/x+y) 已知x²+y²-8x+6y+25=0,求（x-y+4xy/x-y）（x+y-4xy/x+y） 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 3x+2=y 5X+4=Y 7X+6=Y 9X+8=y 11x=y要如何计算 3x+2=y 5x+4=y 7x+6=y 9x+8=y 11x=y y-3x=2,y-5x=4,y-7x=6,y-9x=8,y-11x=0方程组,