Question

Tính nhanh :

 

1978*1979+1980*21+1958

1980*1979-1978*1979

Answer 1

1980*1979-1978*1979

=1979*(1980-1978)

=1979*2

=3957

Answer 2

1980x1979-1978x1979

= 1979x(1980-1978)

= 1979x2

= 3957

Answer 3

1980*1979-1978*1979

=1979*[1980-1978]

=1979*2

=3958

Answer 4

 = 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

Answer 5

=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 :))))