1980*1979-1978*1979
=1979*(1980-1978)
=1979*2
=3957
1980x1979-1978x1979
= 1979x(1980-1978)
= 1979x2
= 3957
1980*1979-1978*1979
=1979*[1980-1978]
=1979*2
=3958
= 1978 x 1979 + ( 1979 + 1 ) x 21 + 1958 / 1979 x ( 1980 - 1979 )
= 1978 x 1979 + 1979 x 21 + 21 + 1985 / 1979 x 2
= 1979 x ( 1978 + 21 + 1 ) / 1979 x 2
= 1978 + 21 + 1 / 2
= 2000 / 2
= 1000
=1978x1979+(1979+1)x21+1958/1979x(1980-1978)
=1978x1979+1979x21+1x21+1958x1/1979x2
=(1978+21)x1979+1x(21+1958)/1979x2
=1999x1979+1x1979/1979x2
=(1999+1)x1979/1979x2
=2000/2
=1000
nếu thấy đúng thì k cho mik nhé :))))
