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Bạn xem lại đề bài nhé. 5 \(\Omega\)5 = 5 + 6 + 7 + 8 + 9
Quy luật của bài này như sau: 3 \(\Omega\)4 là tổng của 4 số liên tiếp bắt đầu từ 3; 5 \(\Omega\)5 là tổng của 5 số liên tiếp bắt đầu từ 5 ->
4\(\Omega\)6 là tổng của 6 số liên tiếp bắt đầu từ 4 -> 4\(\Omega\)6= 4 + 5 + 6 + 7 + 8 + 9 = 39
5 \(\Omega\)5 = 5 + 6 + 7 + 8 + 9
Quy luật của bài này như sau: 3 \(\Omega\)4 là tổng của 4 số liên tiếp bắt đầu từ 3; 5 \(\Omega\)5 là tổng của 5 số liên tiếp bắt đầu từ 5 ->
4\(\Omega\)6 là tổng của 6 số liên tiếp bắt đầu từ 4 -> 4\(\Omega\)6= 4 + 5 + 6 + 7 + 8 + 9 = 39
1+2+3+4+5+6+7+8+9
=(1+9)+(2+8)+(3+7)+(4+6)+5
=10+10+10+10+5
=45
123+546+789=1458
Chúc bạn học giỏi!!!
Nhớ k nha vì mik làm xong đầu đó
1 - 2 + 3 - 4 + 5 - 6 + 7 - 8 + 9
= (9 - 8) + (7 - 6) + (5 - 4) + (3 - 2) + 1
= 1 + 1 + 1 + 1 + 1
= 1 x 5
= 5
10+9-8+7-6+5-4+3-2+1-0
= 10 +[(9 - 8) + (7 - 6) + (5 - 4) + (3 - 2) + (1 - 0)]
= 10 + [1 + 1 + 1 + 1 + 1]
= 10 + 1 x 5
= 10 + 5
= 15
Số số hạng của dãy số là:
10-0+1=11(số)
Tổng của dãy số là: \(\left(10+0\right)\times\frac{11}{2}=10\times\frac{11}{2}=5\times11=55\)
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