40X+30Y=2200 X>20 Y
x+y=450;40%x+30=60%y
x+y=20-6 3x+y=30
|x|+|y|=30 2|x|-3|y|=20 求x,y
(x+y)(x+2y)(x+3y)(x+4y)=-40
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
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,y) |x|+|y|
x>y?x:y
二元函数f(x,y)=x+y/x-y,求f(y/x,x/y)
[x(x-y)-y(x-y)+(x+y)(x-y)]÷2x其中x=2012 y=2013