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(1989.1990+3978):(1992.1991−3984)
=[1989.(1990+2)]:[1992(1991−2)]=(1989.1992):(1992.1989)=1=[1989.(1990+2)]:[1992(1991−2)]=(1989.1992):(1992.1989)=1
\(=\dfrac{1989\left(1990+2\right)}{1992\left(1991-2\right)}=\dfrac{1989}{1989}\cdot\dfrac{1992}{1992}=1\)
a) ( 1989 x 1990 + 3978 ) : ( 1992 x 1991 - 3984 )
= 3 962 088 : 3 962 088
= 1
\(\frac{1989\times1990+3978}{1992\times1991-3984}=\frac{1989\times1990+1989\times2}{1992\times1991-1992\times2}=\frac{1989\times\left(1990+2\right)}{1992\times\left(1991-2\right)}=\frac{1989\times1992}{1992\times1989}=1\)
\(\dfrac{1989\times1990+3978}{1992\times1991-3984}\)
\(=\dfrac{1989\times1990+1989\times2}{1992\times1991-1992\times2}\)
\(=\dfrac{1989\times\left(1990+2\right)}{1992\times\left(1991+2\right)}\)
\(=\dfrac{1989\times1992}{1992\times1989}\)
\(=1\)
a: \(\frac{1989\cdot1990+3978}{1992\cdot1991-3984}\)
\(=\frac{1989\cdot\left(1989+1\right)+3978}{\left(1989+3\right)\left(1989+2\right)-3984}\)
\(=\frac{1989^2+1989+3978}{1989^2+5\cdot1989+6-3984}=\frac{1989^2+5967}{1989^2+5967}\)
=1
b: \(\frac{637\cdot527-189}{526\cdot637+448}\)
\(=\frac{637\cdot526+637-189}{637\cdot526+448}\)
\(=\frac{637\cdot526+448}{637\cdot526+448}\)
=1
Mik sửa lại đề
\(\frac{1989.1990+3978}{1992\cdot1991-3984}\)
Trả lời
\(\frac{1989.1990+3978}{1992.1991-3984}\)
\(=\frac{1989.1990+1989\cdot2}{1992.1991-1992.2}\)
\(=\frac{1989.\left(1992-2\right)}{1992\left(1991-2\right)}\)
\(=\frac{1989.1990}{1992.1989}\)
\(=\frac{1990}{1992}\)
\(=\frac{995}{996}\)
\(\left(1989.1990+3978\right):\left(1992.1991-3984\right)\)
\(=\left[1989.\left(1990+2\right)\right]:\left[1992\left(1991-2\right)\right]=\left(1989.1992\right):\left(1992.1989\right)=1\)
thank you
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
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