“计算(2x^3-3x^2y-xy^2)+(-x^3+2x^2y+y^3)-(x^3-x^2y-xy^2)的值,其中x=

计算3xy[2xy-x(y-2)+x-1] 计算：3xy[2xy-x（y-2）+x] 已知3x*+xy-2y*=0,求(x/y)-(y/x)-(x*+y*)/(xy)的值.*是平方 [x(x^2y^2-xy)-y(x^2-x^3y)]/3x^2y 先化简再求值{(x-y)(x+y)-(x+y)(x-2y)}/y 其中xy的值是代数式{(3x-2y-7)^2+|2x+ 计算：（x^2-y^2/xy)^2/(x+y)^2*(x/x-y)^3 计算3x[xy-2x(1/y-x/3]+3y(x²-y²) (x-2xy)*(-xy+2y*y)-(3x*x-2xy)(x-9xy+6y*y) （x+2y-3xy)-(-2x-y+xy),其中x+y=1/2,xy=-1/2 （x＋2y-3xy）-（-2x-y+xy）,其中x+y=,xy=-,求值. 1、(-7x^y)(2x^y-3xy^3+xy) 2、((x-y)^6)/((y-x)^3)/(x-y) 化简：x-y/x+3y÷x^-y^2/x^2+6xy+9y^2-(xy/x+y)