4(x-1)=2(1-x) y-y-1/2=3-y+2/5 3y-1/2-5y+1/3=1-7y+1/6 谢谢

化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 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 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-( 微分方程(1)(y'')^2+5y'-y+x=0;(2)y''+5y'+4y^2-8x=0;(3)(3x+2y)dx+( x+y=3 x+2y=9 3/x+1=y y-x=3 y=2x-3 y-3x=1 2(x+1)-y=6 7x-5y=-9 3x+2y/4=2x+y/5=x-y+1/6 [(2x+y)^2+(y+2x)(y-2x)-2y(4x-y)]/4y,其中x=1/2,y=1/3 (3x-y)^2+(3x+y)(3x-y),x=1,y=-2 （x+2)(x+3) (x-4)(x+1) (y+4)(y-2) (y-5)(y-3) 先化简,再求值：[(x+y)(x-y)-(x-y)^2+2y(x-3y)]/(-4y),其中x=1,y=-2 3x-2y=1 4x-5y