若4x^2+9y^2-12xy-4x-4y-8小于等于0,且x,y是实数,则有（ ）x + y 的最小值是 -2请主要描述一下解题思路、过程,

因式分解:12xy^2(y-x)+xy^3(x-y)+4x^2y(x-y) 已知X+Y=3,XY=-1,求2(X-Y)^4-9(X-Y)^2+12XY 若x+y=4,x^3+y^3=(x+y)(x^2-xy+y^2)z,求x^3+12xy+y^3的值. (x^2+2xy+y^2-4xy)*(x^2-2xy+y^2+4xy) 化简:-x(2)-(2xy) *9x(2)-9xy(3)+12x(4)y(2)/(3xy)谢谢! (x+y)(x+y+2xy)+(xy+1)(xy-1)(x+y)(x-y)+4(y-1) 4x^2y+12xy+9y分解因式 9-x^2-y^2+4xy 9-x^2-y^2+4xy, 若x-y=4,xy=1,求(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 若x-y=4,xy=1,则(2x+y-2xy)-(3x+2y+xy)-(4xy+3y-5x)= (x^-4y^)/(x^+2xy+y^)/(x+2y)/(2x^+2xy) 因式分解 x-xy+3y-3x 2x+xy-y-4x+5y-6 化简：3x^2-[5xy-(x^y-3xy)+4x^2y-8xy] （-3x^y+2xy)-( )=4x^+xy 2x(x-y)+4xy(y-x) 因式分解2x(x-y)+4xy(y-x) 因式分解 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 若3x^2+xy-2y^2=0,求（x+y/x-y+4xy/y^2-x^2)除以(x^2+2xy-3y^2/x^2-9y^2)的值