a-1的绝对值与b+1/2的平方互为相反数
所以有:|a-1|+(b+1/2)^2=0
即a-1=0,b+1/2=0
得a=1,b=-1/2
(a+b)^2+(a-b)(a+b)
=(1-1/2)^2+(1+1/2)(1-1/2)
=1/4+3/4
=1