Tính nhanh: (–25) . (75 – 45) – 75 . (45 – 25
Câu 13: Tính nhanh: (–25) . (75 – 45) – 75 . (45 – 25).
Câu 13: Tính nhanh: (–25) . (75 – 45) – 75 . (45 – 25).
Ta có
(–25) . (75 – 45) – 75 . (45 – 25)
= –25 . 75 – (–25) . 45 – 75 . 45 – (–75) . 25
= –25 . 75 + 25 . 45 – 75 . 45 + 75 . 25
= 75 . (–25 + 25) + 45 . (25 – 75)
= 75 . 0 + 45 . (–50)
= 0 + (–2250 )
= –2250.