c^2+2 |a-1|+根号{(2b+c+1)/(4-c) =0
c^2≥0,2 |a-1|≥0,根号{(2b+c+1)/(4-c) ≥0
c^2=0,a-1=0,(2b+c+1)/(4-c) =0
a=1,b=-1/2,c=0
a+b+c=1-1/2+0=1/2