{2X-5Y=-3,5X-2Y=-18
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{2X-5Y=-3,5X-2Y=-18
2X-5Y=-3(1) 5X-2Y=-18(2) (1)*5 10x-25y=-15(3) (2)*2 10x-4y=-36(4) (3)-(4) -21y=21 y=-1 代入(1) x=-4 所以x=-4 y=-1
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
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
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)+...-(
数学题……555{(3x+y)(3x-y)-(x-5y)(5x-y)-(x-2y)²÷(-4x),x=-2.y
(4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuai
5(x+y-2)=3-y
5x=3y,(2x+y)的平方=5x(x+y)+9
3x-2y=9 x-3y=2 x+y=5 x+2y=3 y=x 2x+y=8
若3x-5y=0,则x+y/x=(),x-y/y=(),2x-3y/2x+3y=( )