Question

46. Calculati: a) 3 +6+ 9 + 12 + ... +2019; c) 5+ 10 + 15 + 20 + ... + 2 020; b) 4 + 8 + 12 + ... +2020; d) 7 +14+ 21 + ... +2023..Va rog,dau coroana,urgent!
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Answer 1

Explicație pas cu pas:

a) 3+6+9+12+....+2019=

=(2019+3)×[(2019-3):3+1]:2

=2021×(2016:3+1):2

=2021×(672+1):2

=2021×673:2

=1 358 112:2

=679 056

b)5+10+15+20+......+2020=

=(2020+5)×[(2020-5):5+1]:2

=2025×(2015:5+1):2

=2025×(403+1):2

=2025×404:2

=2025×202

=409 050

c)4+8+12+....+2020=

=(2020+4)×[(2020-4):4+1]:2

=2024×(2016:4+1):2

=2024×(504+1):2

=2024×505:2

=1 022 120:2

=511 060

d)7+14+21+....+2023=

=(2023+7)×[(2023-7):7+1]:2

=2030×(2016:7+1):2

=2030×(288+1):2

=2030×289:2

=584 640:2

=292 320

Sper că te-am ajutat! Spor!