已知a+b=3,ab=2 (1)a-b

问题描述:

已知a+b=3,ab=2 (1)a-b

(a-b)²
=a²-2ab+b²
=a²+2ab+b²-4ab
=(a+b)²-4ab
=9-8
=1
∴a-b=1或a-b=-1