Cgcr

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

Tính nhanh: 1+2+3+4+5+6+7-1+2+3+4+5+6+7 = 0

1+2+3+4+5+6+7-1+2+3+4+5+6+7

=(1+2+3+4+5+6+7)-(1+2+3+4+5+6+7)

Ve 1 bang ve 2=>ve 1 - ve 2= 0

Dap an bang 0

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

5

5+6+7+8+9

=35

5+6+7+8+9+10

=45

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

máy tính đâu

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

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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a) x.4/5:2=6/7                                                              

    x.4/5=6/7*2

    x.4/5=12/7

    x=12/7:4/5

    x=15/7

b) 6/5:x:5/4=10/15

    6/5:x=10/15*5/4

    6/5:x=5/6

    x=6/5:5/6

    x=36/25