1+3+9=13

1 + 3 + 9 = 13 nha

1+3+9=13

A=\(\frac{1}{2}.\frac{2}{3}.\frac{3}{4}...\frac{2014}{2015}.\frac{2015}{2016}\)

A=\(\frac{1.2.3.4...2015}{2.3.4...2016}=\frac{1}{2016}\)

Hok tốt

A = \(\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right)...\left(1-\frac{1}{2015}\right).\left(1-\frac{1}{2016}\right)\)

= \(\frac{1}{2}.\frac{2}{3}.\frac{3}{4}...\frac{2014}{2015}.\frac{2015}{2016}\)

= \(\frac{1}{2016}\)

Vậy ...

\(A=\left(1-\frac{1}{2}\right)\left(1-\frac{1}{3}\right)\left(1-\frac{1}{4}\right)......\left(1-\frac{1}{2015}\right)\left(1-\frac{1}{2016}\right)\)

\(\Rightarrow A=\frac{1.2.3.4....2015}{2.3.4....2016}\)

\(\Rightarrow A=\frac{1}{2016}\)

#hok tốt

8 + 9 x 2

= 8 + 18

=26

Tk cho mk nhé , Dương Nhật Ánh !

8 + 9 x 2

= 8 + 18

= 26

bạn gửi kết ban với mình nhé . k mình mình trả lời nhanh nhất

8 + 9 * 2 = 8 + 18 

             = 26

k cho mk nha !

#)Giải :

\(\left[\left(-\frac{56}{64}\right)--\left(\frac{1}{9}\div\frac{8}{27}\right)-\frac{1}{3}\right]\div-\frac{81}{128}\)

\(\Leftrightarrow\left[\left(-\frac{7}{8}\right)-\left(-\frac{3}{8}\right)-\frac{1}{3}\right]\div\left(-\frac{81}{128}\right)\)

\(\Leftrightarrow\left(-\frac{5}{6}\right)\div\left(-\frac{81}{128}\right)\)

\(\Leftrightarrow\frac{320}{243}\)

Tham khảo :https://h.vn/hoi-dap/question/692888.html

Hoặc hỏi trên H.vn 

  \(\left[-\frac{54}{64}--\left(\frac{1}{9}:\frac{8}{27}\right):-\frac{1}{3}\right]:-\frac{81}{128}\)

\(=\left[-\frac{54}{64}+\frac{3}{8}:-\frac{1}{3}\right]:-\frac{81}{128}\)

\(=\left[-\frac{54}{64}-\frac{9}{8}\right]:-\frac{81}{128}\)

\(=-\frac{63}{32}:-\frac{81}{128}\)

\(=\frac{28}{9}\)

số nào nhân 0 chả =0

HT

chúc bn năm mới vui vẻ

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0 nha

T i c k mik nha

(1+2+3+4+5+..........+99999999999999999)x0=0

HT

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bằng 83/90

\(\frac{1}{2}+\frac{1}{5}+\frac{2}{9}\)

=\(\frac{45}{90}+\frac{18}{90}+\frac{20}{90}\)

=\(\frac{83}{90}\)

\(\frac{1}{2}+\frac{1}{5}+\frac{2}{9}=\frac{1}{2}_{\left(45\right)}+\frac{1}{5}_{\left(18\right)}+\frac{2}{9}_{10}\)

\(=\frac{45}{90}+\frac{18}{90}+\frac{20}{90}=\frac{45+18+20}{90}\)

\(=\frac{83}{90}\)

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 

= ( 1 + 9 ) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + 5 

= 10 + 10 + 10 + 10 + 5

= 10 x 4 + 5 

= 40 + 5 = 45

Lê Thị Thanh Ngọc

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 

= ( 1 + 9 ) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) +5

=     10         +       10       +     10        +         +10 +5

= 10 x 4 + 5 

= 45

1+2+3+4+5+6+7+8+9=45