1980.1979-1978.1979
=(1980-1978)x1979
=2x1979
=3958
1978.1979+1980.21+1958
=3914462+41580+1958
=3956042+1958
=3956240
1980.1979-1978.1979
=3918420-3914462
=3958
li-ke cho mình nha
\(\frac{1978.1979+1980.21+1958}{1980.1979-1978.1979}\)=\(\frac{1978.1979+1979.21+21+1958}{1979.\left(1980-1978\right)}\)
=\(\frac{1979.\left(1978+21\right)+21+1958}{1979.2}\)= \(\frac{1979.\left(1978+21+1\right)}{1979.2}\)
=\(\frac{1979.2000}{1979.2}=1000\)
Vậy = 1000