5x+5*4/7x=y*2 5*x+5y=0

解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7 {6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 x*x+2x+y*y-4y+5=0 x= y= 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 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) 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 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 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 把(x-y)看作一个整体,化解:5(x-y)+2(x-y)-4(x-y)= 3(x-y)把(x-y)看作一个整体,化解:5(x-y)+2(x-y)-4(x-y)=3(x-y)²-4(x-y)+7(x-y)-6(x-y)²= 5x-4y(y-x)=? 4x+2y-5x-y 因式分解(x-2y)(x-3y)+(x-4y)(x-5y)+（x-3y)(x-5y)+(x-2y)(x-4y) 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 把(x-y)看做一个整体,合并同类项5(x-y)+2(x-y)-4(x-y)=3(x-y)次方-4(x-y)+7(x-y)-6(x-y)次方= 化简求值：2(x+y)(x-2y)-2x(x+y),其中x、y满足x^2+y^2-2x+4y=-5