{x/2=y/5 {25%x+40%y=1.4

已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y (x+y)(x+2y)(x+3y)(x+4y)=-40 2x+3y=40x-y=-5 解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 x-y / 5y= (y-x)^2 / ( ) {x/2=y/5 {25%x+40%y=1.4 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 5(x-y)^3*[-6/25(y-x)^3][-2/3(y-x^4]= [x(x-y)-y(x-y)+(x+y)(x-y)]÷2x其中x=2012 y=2013