解x^2+y^2-4x-2y-20=0变成圆的标准方程,一步一步计算

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 y=-cosx怎样变到y=sin(2x+4分之x) 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 x*x+2x+y*y-4y+5=0 x= y= 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y*y)的值 X^4-5X^2+4Y^4怎么变化成(X+Y)(X-Y)(X+2Y)(X-2Y)这步?就算是把(X+Y)(X-Y)(X+2Y)(X-2Y)算出来 也是=（X^2-Y^2)(X^2-4Y^2)=X^4-5X^2Y^2+4Y^4...也不是=(X^4-5X^2+4Y^4) 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 解方程组x^2-y^2=x+y 4x^2-y^2+2x-y=0过程 x^2+y^2-2x+4y-20=0则y/x的最大值,x+y的最大值 解方程组;x+y/2=x-y/3=6 4(x+y)-3(x-y)=-20 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= (x-4y)(2x+y)= 先化简再求值; 解方程组 x(x-y)-y(x+y)+2xy 其中x=2 ,y=-22.x[x-x(x-1)],其中x=-2解方程组4x+3y=12x-y=32.y+1=2x 4x-y=2 3.2x+2y=0 2x-y+24=0 六年级三道关于方程的数学题. 解方程组{-x+2y+3z=12 {2x-2y+5z=13 {3x+2y+z=10 解方程组{2(x+y)-3(x-y)=1 {6(x+y)+7(x-y)=51 此题去括号,变简易方程组再做.已知方程组{2x-y=0 {2x+y=m 和方程组{x-y=5 {2x-y=n-1 x*x+y*y-2x+4y+5=0求x,