问题
填空题
若a-b=-1,ab=2,则(a+1)(b-1)=______.
答案
(a+1)(b-1)
=ab-a+b-1
=ab-(a-b)-1
把a-b=-1,ab=2代入上式得:
=2-(-1)-1
=2+1-1
=2.
故答案为:2.
若a-b=-1,ab=2,则(a+1)(b-1)=______.
(a+1)(b-1)
=ab-a+b-1
=ab-(a-b)-1
把a-b=-1,ab=2代入上式得:
=2-(-1)-1
=2+1-1
=2.
故答案为:2.