tính nhanh: 1978 x 1979 + 1980 x 21 + 1958
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cọc a ko bik làm :)))
b) 1980 x 1979 - 1978 x 1979
= ( 1980 - 1978 ) x 1979
= 2 x 1979
= 3958
Chúc bạn hok tốt!~~~
b) 1980 . 1979 - 1978 . 1979
= 1979 ( 1980 - 1978 )
=1979 . 2
= 3958
=))
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1000 đó bạn ơi chuẩn 10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000%luôn đó bạn
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1987 x 1979 + 1980 x 21 + 1958 / 1980 x 1979 - 1978 x 1979
= 1987 x 21 + 1958 / 1979 - 1978
= 41727 + 1958 / 1
= 43685 / 1 = 43685
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a ) ( 1978 x 1979 + 1980 x 21 + 1958 ) / ( 1980 x 1979 - 1978 x 1979 ) = 1978 x 1979 + 1980 / 1979 . ( 1980 - 1978 )
= 0/1979
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\(\frac{1978\cdot1979+1980\cdot21+1958}{1980\cdot1979-1978\cdot1979}=\frac{1978\cdot1979+\left(1979+1\right)\cdot21+1958}{1979\cdot\left(1980-1978\right)}\)
\(=\frac{1978\cdot1979+1979\cdot21+21+1958}{1979\cdot2}=\frac{1979\cdot\left(1978+21+1\right)}{1979\cdot2}=\frac{2000}{2}=1000\)
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