a²-ab-b²=﹣3/4,a²-ab+2b²=2/3,求b

问题描述:

a²-ab-b²=﹣3/4,a²-ab+2b²=2/3,求b

a²-ab-b²=﹣3/4,(1)
a²-ab+2b²=2/3 (2)
(2)-(1)
3b²=(3/4)+(2/3)=17/12
b=±√17/6