Bài 108 trang 98 SGK toán 6
Đề bài
Cho số nguyên a khác 0. So sánh -a với a, -a với 0
Giải.
- Nếu a > 0 thì –a < a và –a < 0.
- Nếu a < 0 thì –a > a và –a > 0.
Bài 111 trang 99 SGK 6
Đề bài
Tính các tổng sau:
a) [(−13)+(−15)]+(−8)[(−13)+(−15)]+(−8)
b) 500–(−200)–210−100500–(−200)–210−100
c) –(−129)+(−119)−301+12–(−129)+(−119)−301+12
d) 777–(−111)–(−222)+20
Giải.
a) (–13)+(–15)+(–8)(–13)+(–15)+(–8)
=–(13+5+8)=–(13+5+8)
=–36.=–36.
b) 500–(–200)–210–100500–(–200)–210–100
=500+200–210–100=500+200–210–100
=500+200–(210+100)=500+200–(210+100)
=700–310=390.=700–310=390.
c) –(–129)+(–119)–301+12–(–129)+(–119)–301+12
=129–119–301+12=129–119–301+12
=(129+12)–(119+301)=(129+12)–(119+301)
=141–420=141–420
=–279.=–279.
d) 777–(–111)–(–222)+20777–(–111)–(–222)+20
=777+111+222+20=777+111+222+20
=(777+111+222)+20=(777+111+222)+20
=1110+20=1130.
