化简 (x^2+2y^2)(x-2y)+2xy（x-y)

因式分解：x×x-xy-2y×y-x-y 化简：x-y/x+3y÷x^-y^2/x^2+6xy+9y^2-(xy/x+y) （x^2+xy/x-y)/（xy/x-y)计算 （xy-x^2)乘以(xy)/(x-y) 化简(x平方-y平方)/(x+y)+(x平方-2xy+y平方)/(x-y) 作乘法:(x+y)(x^2-xy+y^2)；(x-y)(x^2+xy+y^2) x根号x+x根号y/xy-y^2)-（x+根号xy+y/x根号x-y根号）y [x(x^2y^2-xy)-y(x^2-x^3y)]/3x^2y 2xy/(x+y)(x+y)与x/(x+y)(x-y)怎么通分 (x+y)(x-y)-(2xy+3y)平方 (x+y-2xy)(x+y-2)+(1-xy)² (x^2-xy)y÷y-x/xy怎么做?