知|a-2b-4|+(2a+b+1)²=0,求a+b
a-2b-4= 0
2a+b+1 = 0 4a+2b+2 =0
5a =2
a= 2/5
b = -1 - 4/5 = 9/5
a+b = ( 2+9)/5 = 11/5