{x+y=1000① 20x+30y=26000②
x+y=20-6 3x+y=30
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
|x|+|y|=30 2|x|-3|y|=20 求x,y
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二元函数f(x,y)=x+y/x-y,求f(y/x,x/y)
有这样一道题,计算:(x-y)[(x+y)(x+y)-xy]-(x-y)[(x-y)(x-y)+xy]的值,其中x=20
[x(x-y)-y(x-y)+(x+y)(x-y)]÷2x其中x=2012 y=2013
① X+Y=3 Y=2X-3 ② x+2y=9 y-3x=1 ③3/x+1=y 2(x+1)=6 ④ y-x=3 7x-
下列函数:①y=-3x②y=2x-1;③y=-1/x(x