Tính: (-57).(67 - 34) - 67.(34 - 57)

* Hướng dẫn giải

*Cách 1:

(–57) . (67 – 34) – 67 . (34 –57)

= [(–57) . 67 – (–57 ) . 34] – (67 . 34 – 67 . 57)

= – (57 . 67) – [–(57 . 34)] – (67 . 34 – 67 . 57)

= – 57 . 67 + 57 . 34 – 67 . 34 + 67 . 57

= 67 . 57 – 57. 67 + 57 . 34 – 67 . 34

= 0 + 34 . (57 – 67)

= 34 . (–10) = –340

*Cách 2:

(–57) . (67 – 34) – 67 . (34 –57)

= (–57) . 33 – 67 . (-23)

= -1881 + 1541

= -340