{x+1=5(y+2) {3(2x-5)-4(3y+4)=5

化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-( 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 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 3x-2y=1 4x-5y 数学题……555{(3x+y)(3x-y)-(x-5y)(5x-y)-(x-2y)²÷(-4x),x=-2.y （x+2)(x+3) (x-4)(x+1) (y+4)(y-2) (y-5)(y-3) (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuai 化简求值{(x=2y)(5x-2y)-(3x+2y)(3x-2y)]/4x,其中x=2,y=-1 3x+2y/4=2x+y/5=x-y+1/6 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 微分方程(1)(y'')^2+5y'-y+x=0;(2)y''+5y'+4y^2-8x=0;(3)(3x+2y)dx+(