a(a-1)-(a2-b)=2,求ab-二分之a2+b2

问题描述:

a(a-1)-(a2-b)=2,求ab-二分之a2+b2

a(a-1)-(a²-b)=2 a²-a-a²+b=2 -a+b=2 ab-(a²+b²)/2=-½(a²+b²-2ab)=-½(a-b)²把-a+b=2代入上式=-½×(-2)²=-2 答案:-2