以下哪些为圆的方程?3x^2+3y^2-5x+4y-6=0(x-2)^2+(y+5)^2=8x^2-y^2=42x^2+

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 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= 解方程x+y+(x+y/2)=15 3x+5y+4(x+y/2)=62 求方程x+2y-3x=4,3x-2y+x=6,3x+2y-5x=8的解 (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuai 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