\(\frac{1989\cdot1990+3878}{1992\cdot1991-3984}=\frac{1989\cdot1990+1989\cdot2}{1992\cdot1991-1992\cdot2}=\frac{1989\cdot(1990-2)}{1992\cdot(1991-2)}=\frac{1989\cdot1992}{1992\cdot1989}=1\)
Bằng 1 nha bạn
1989.1990+3978 / 1992.1991-3984
= 1989.1990+1989x2 / 1992.1991-1992x2
= 1989.(1990-2) / 1992.(1991-2)
= 1989.1992 / 1992.1989
= 1
\(\frac{1989.1990+3878}{1992.1991-3984}\)
\(=\frac{1989.1990+1989.2}{1992.1991-1992.2}\)
\(=\frac{1989.\left(1990+2\right)}{1992.\left(1991-2\right)}\)
\(=\frac{1989.1992}{1992.1989}\)
\(=1\)
