4a^2+b^2+4a=2b-2
4a^2+4a+1+b^2-2b+1=0
(2a+1)²+(b-1)²=0
平方数均为非负数,只能均为0
因此a=-0.5,b=1
/(-4a)
=(9a²-b²+b²)/(-4a)
=-9a/4
=9/8