化简2(4x-6y)-3(2x+3y-1) ,化简1÷2（2x－4y）＋2y ,

化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 已知x－y＝1,y≠0,求｛(x＋2y)²＋（2x＋y）(x＋4y)－3(x＋y）（x－y)｝÷y的值. 1.（（y+2x)(-2x+y)+4(x+2y)^2)/3y 2.（2(x-y)^3-8(x-y）^2(x+y)+6y( 化简：[(2x-y)平方+（2x+y)(2x-y)-4x(x-y+1)]÷2x （x+2)(x+3) (x-4)(x+1) (y+4)(y-2) (y-5)(y-3) 化简:(x-3y)(x+y)-(x-2y)(x+2y)-(x-y)平方 化简：x-y/x+3y÷x^-y^2/x^2+6xy+9y^2-(xy/x+y) 因式分解 (1)6(x-y)^3-3y(y-x)^2 (2)x(x-y)(a-b)-y(y-x)( 化简(x+y)-(2x+y/2)-(3x+y/6)-(4x+y/12)-(5x+y/20)-……-(10x+y/90) 化简,并求值2(x-2y)²-4（x+3y)(x-3y)-2(x-y).(y+x)-5(-x-1)² 计算:1/(x-y)-1/(x+y)-2y/(x^2+y^2)-4y^3/(x^4+y^4)-8x^7/(x^8+y^8