【1】x^2y-5xy^2+4x^2y-2xy^2 【2】-3mn+2mn-5mn 【3】-3a^2+2a-1+a^2-5a-8

(x+y)(x+y+2xy)+(xy+1)(xy-1)(x+y)(x-y)+4(y-1) x²-y²+5x+3y+4（x+y-2xy)(x+y-z)+(xy-1）² 因式分解 x-xy+3y-3x 2x+xy-y-4x+5y-6 (-2xy+2x+5y)-(3xy+2y-2x)-(x+4y+xy)其中x-y=4xy=-1 若x-y=4,xy=1,则(2x+y-2xy)-(3x+2y+xy)-(4xy+3y-5x)= 化简：3x^2-[5xy-(x^y-3xy)+4x^2y-8xy] 计算：（1）8x^2y^2*(-3x/4y^5) (2)(x+y)^2/xy-y^2*(y-x)^2/xy+y^2 因式分解:12xy^2(y-x)+xy^3(x-y)+4x^2y(x-y) .(x+y-2)(x+y-2xy)+(xy-1)^2 4xy-[(x²+5xy-y²)-(3xy-1/2y)]x=3,y=-6 x²/xy-x/y 3x/4x+y - x-2y/4x+y (1-y/y+x)÷x/y²-x² 2X^+XY-Y^-4X+5Y-6 2x^+xy-y^-4x+5y-6=? x-y/x^2+xy除以xy-x^2/x^2y^2-x^4*1/x-y 已知1/x+1/y=5,求x+y+3xy/2x-4xy+2y的值,已知1/x+1/y=5,x+y+3xy/2x-4xy+2y的值, 5xy平方-2x平方y+[3xy平方-(4xy-2x平方y-2x平方y)],其中x=-2,y=-1求值 化简:[4xy(x-y)^-1 + (xy^-1 - x^-1y)/(x^-1 + y^-1)] / (x+y)^2 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