4xy+3x=56 5xy+2x=78

（-3x^y+2xy)-( )=4x^+xy 先化简,再求值 ⒈2(Xy+Xy)-3(Xy-xy)-4Xy,其中X=1,y=-1 已知x-y=4xy，则2x+3xy-2yx-2xy-y 化简:xy分之3x^2+2xy-xy分之2x^2-xy= 已知x^2-xy=5,xy-y^2=-3求3(x^2-xy)-xy+y^2 x+y=8,xy=-2,求(5xy+4x+7y)+(6x-3xy)-(4xy-3y)的值 x*-2xy+3y*=9 4x*-5xy+6y*=30 [3xy(1-x)-6xy(x-1/2)]*2x*(-xy)平方,x=-1 y=2 ； 3xy平方（-1/3x平方y+4 已知xy^2=-2,求-xy（x^2y^5-xy^3-y)的值. 已知xy^2=-2 求-xy(x^2y^5-xy^3-y) 已知A=5x^2y-3xy^2+4xy,B=7xy^2-2xy+x^2y. 已知a=5x的平方y-3xy的平方+4xy,b=7xy的平方-2xy+x的平方y.