A={(x,y)|x+y≤1,且x≥0,y≥0].(A打漏.)
A:1≤x≤1,0≤y≤1-x.
B:0≤x+y≤1.-(x+y)≤x-y≤x+y,
在xoy,成为:0≤x≤1,-x≤y≤x,(图中⊿O′A′B′).面积=1.
[-(x+y)≤x-y≤x+y之得来:0≤y,∴-y≤y,∴x-y≤x+y.
0≤x,∴-x≤x,∴-(x+y)=-x-y≤x-y.即-(x+y)≤x-y≤x+y]
A={(x,y)|x+y≤1,且x≥0,y≥0].(A打漏.)
A:1≤x≤1,0≤y≤1-x.
B:0≤x+y≤1.-(x+y)≤x-y≤x+y,
在xoy,成为:0≤x≤1,-x≤y≤x,(图中⊿O′A′B′).面积=1.
[-(x+y)≤x-y≤x+y之得来:0≤y,∴-y≤y,∴x-y≤x+y.
0≤x,∴-x≤x,∴-(x+y)=-x-y≤x-y.即-(x+y)≤x-y≤x+y]