\(=\dfrac{1989\left(1990+2\right)}{1992\left(1991-2\right)}=\dfrac{1989}{1989}\cdot\dfrac{1992}{1992}=1\)

$\left(1989.1990+3978\right):\left(1992.1991-3984\right)$

$=\left[1989.\left(1990+2\right)\right]:\left[1992\left(1991-2\right)\right]=\left(1989.1992\right):\left(1992.1989\right)=1$

\(\left(1989.1990+3978\right):\left(1992.1991-3984\right)\)

\(=\left[1989.\left(1990+2\right)\right]:\left[1992\left(1991-2\right)\right]=\left(1989.1992\right):\left(1992.1989\right)=1\)

1989 . 1990 + 3978 1992 . 1991 − 3984  ⇒  1989 . 1990 + 1989 . 2 1992 . 1991 − 1992 . 2  ⇒  1989 . ( 1990 + 2 ) 1992 . ( 1991 + 2 )    ⇒  1989 . 1992 1992 . 1989  ⇒  1

dấu chấm là dấu nhân

\(\dfrac{1989\times1990+3978}{1992\times1991-3984}\)

\(=\dfrac{1989\times1990+1989\times2}{1992\times1991-1992\times2}\)

\(=\dfrac{1989\times\left(1990+2\right)}{1992\times\left(1991+2\right)}\)

\(=\dfrac{1989\times1992}{1992\times1989}\)

\(=1\)

\(\left(1989\times1990+3978\right):\left(1992\times1991-3984\right)\\ =\left(1989\times1990+1989\times2\right):\left(1992\times1991-1992\times2\right)\\ =\left(1989\times1992\right):\left(1992\times1989\right)\\ =1\)

\(\frac{1989\times1990+3978}{1992\times1991-3984}=\frac{1989\times1990+1989\times2}{1992\times1991-1992\times2}=\frac{1989\times\left(1990+2\right)}{1992\times\left(1991-2\right)}=\frac{1989\times1992}{1992\times1989}=1\)

Đáp số: 1.

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Ai tk cho mình mình tk lại.

bằng 1 nha!

kujg989j

b=0 nha

= 1 nhé bn

a) ( 1989 x 1990 + 3978 ) : ( 1992 x 1991 - 3984 )

= 3 962 088 : 3 962 088

= 1