x+2y=3(x+y)+5 3x-4y=4(x+y)-15
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x+2y=3(x+y)+53x-4y=4(x+y)-15x+2y=3(x+y)+53x-4y=4(x+y)-15x+2y=3(x+y)+53x-4y=4(x+y)-15x+2y=3(x+y)+5x+2
x+2y=3(x+y)+5 3x-4y=4(x+y)-15
x+2y=3(x+y)+5 3x-4y=4(x+y)-15
x+2y=3(x+y)+5 3x-4y=4(x+y)-15
x+2y=3(x+y)+5
x+2y=3x+3y+5
2x+y=-5 (1)
3x-4y=4(x+y)-15
3x-4y=4x+4y-15
x+8y=15 (2)
(1)×8-(2)
16x-x=-40-15
15x=-55
所以x=-11/3
y=-5-2x=7/3
an=2^(n-1)/3^n
=1/2*(2/3)^n
所以Sn=1/2*[2/3+4/9+……+(2/3)^n]
=1/2*2/3*[1-(2/3)^n]/(1-2/3)
=1-(2/3)^n
3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2
4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11
3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27
(x+y)/2- x-y/2=6 3(x+y)=4(x-y)
先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5
(x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)=
已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1
(x+y-5)*(x+y-5)+(x-y+3)=0 x*x-y*y
x+2y=3(x+y)+5 3x-4y=4(x+y)-15
已知:3x-5y=0,求x/y,x-y/y,x-y/x
(4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuaihuajian
先化简,再求值 [2/3x - 2/x+y(x+y/3x -x-y)]*x/x-y,其中5x+3y=0
(5x+3y)(3y-5x)-(4x-y)(4y+x)=
2(x+y)-3(x-y)=3 ,4(x+y)+3(x-y)=15
3X=5Y (X+Y)*3X=(2Y+X)*4+2*2
x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20
{(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20