(1)2x-y=3 5x+2y=-6 (2)2/3x-1/2y=-1 1/2x+1/5y=5
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
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)=4 {x+y/2 + x-y/6=1
(2x+y-1)(2x-y+1)-(3x+y)(3x-y),其中x=5分之1,
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
x+y/2+x-y/3=5/6;x=y/6-x-y/3=1/2
3x+2y/4=2x+y/5=x-y+1/6
(3x-y)^2+(3x+y)(3x-y),x=1,y=-2
3X+5y=2 x+y=1
3x-2y=1 4x-5y
化简求值(x+2y)^2-(2x+y)(2x-y)-5y(y-x) 其中 x=1/3 y= -1/2