x^3+x+30x^2-4xy+4y^2+7x-14y+12

xy=-2,x+y=3,求代数式（4xy+12y)+[7x-(3xy+4y-x)] 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) x^8-x^7y+x^6y^2-x^5y^3+x^4y^4-x^3y^5+x^2y^-xy^7+y^8 x^3y(-4y)^2+(-7xy)^2*(-xy)-5xy^3*(-3x)^2 （-3x^y+2xy)-( )=4x^+xy 已知3x^2+xy-2y^2=0,求{(x+y)/(x-y)+4xy/(y^2-x^2)}/{(x+3y)*(x-y)} (x^-4y^)/(x^+2xy+y^)/(x+2y)/(2x^+2xy) 1、(-7x^y)(2x^y-3xy^3+xy) 2、((x-y)^6)/((y-x)^3)/(x-y) 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? (2x-y)(2x+y)+(2x-y)(y-4x)+2y(y-3x)+2x^4y^2÷(xy)^2 x^2y+4xy+4y -3xy(x^2-2x-1)+(2x-3y)(3x-4y)=?