已知点M(a,b)在由不等式组【x>=0,y>=0,x+y

题目

已知点M(a,b)在由不等式组【x>=0,y>=0,x+y

答案

设a+b=x,a-b=y,则
a=(x+y)/2,b=(x-y)/2,
依题意(x+y)/2>=0,(x-y)/2>=0,(x+y)/2+(x-y)/2=0,x-y>=0,x