Bai63 ; khong lam phep tinh hay cho biet chu so tan cung cua moi ket qua sau;
1. (1981+1982+1983+....+1989)-(21*23*25*27)
A.0 B.5 C.2
2. 32*44*75*69-21*39*63*55
A.0 B.1 C.5
Bai 64 ;ban co the cat 5 hinh tam giac vuong bang nhau dung 5 tam giac vuong nay ghep lai thanh 1 hinh tam giac vuong duoc khong?
1/ B
2/ A
\(\text{1,B 2,A}\)