计算：(1/4x^2-xy+y^2)/(x-2y)

（x^2+xy/x-y)/（xy/x-y)计算 计算3xy[2xy-x(y-2)+x-1] 计算:(x-2y)(1+x+2y+4y^2+2xy+x^2) x-y/xy-y^2计算 计算:4xy-(x+y)^2/xy(x+y)(x-y)÷x^2+xy-2y^2/x^2y+2xy^2 计算：(x+y/x-y)÷(xy+x^2) 计算3x[xy-2x(1/y-x/3]+3y(x²-y²) 计算：(5-xy/x^3-x^2y)/(1-5/xy)^2*(y-x)^3 计算（xy-y^2)÷x-y/xy 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) 计算4xy+（x-2y）的平方+(x+3y)(3y-x) 计算：3xy[2xy-x（y-2）+x]