x+y=20 5x-2y=58x+y=205x-2y=58
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x+y=20 5x-2y=58x+y=205x-2y=58
x+y=20 5x-2y=58
x+y=20
5x-2y=58
x+y=20 5x-2y=58x+y=205x-2y=58
x+y=20①
5x-2y=58②
①*2+②
2x+2y+5x-2y=20*2+58
7x=98
x=14
代入①得
14+y=20
y=6
∴{x=14
{y=6
x=20-y
5(20-y)-2y=58
100-5y-2y=58
7y=100-58
7y=42
y=6
x y=20①
5x-2y=58②
①*2 ②
2x 2y 5x-2y=20*2 58
7x=98
x=14
代入①得
14 y=20
y=6
∴{x=14
{y=6
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x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2
已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
x+y=20 5x-2y=58x+y=205x-2y=58
2(x-y)=5y,x-y=-5
x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2
x-y / 5y= (y-x)^2 / ( )
x*x+2x+y*y-4y+5=0 x= y=
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
4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6
解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7
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
{6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1
6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5
求(X+Y)(X-Y)(X²+Y²),X=5 Y=2,
(x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5)