已知a＋b＝3，且a－b＝－1，则a2＋b2＝ 。
5
由a＋b＝3，a－b＝－1可解得，故a2＋b2＝5
I hesitated for a moment before choosing, otherwise, I the mistake. [ ]
A. had made
B. made
C. would make
D. would have made
《四书》是指？
，故a2＋b2＝5
，故a2＋b2＝5