2a-b+1=0
3a+3b/2=0
解这个方程组得
a=-1/4
b=1/2
(b2/a+b)/(a/a-b-1)/(ab-a2/a+b) 加了一个b
=b²/(a+b)÷[a-(a-b)]/(a-b)÷a(1-a)/(a+b)
=b²/(a+b)*(a-b)/b*(a+b)/a(b-a)
=-b/a
=2