Ta có: \(\dfrac{-5}{13}\cdot\dfrac{3}{7}-\dfrac{2}{17}\cdot\dfrac{8}{13}+\dfrac{5}{13}\cdot\dfrac{1}{7}\)

\(=\dfrac{5}{13}\left(-\dfrac{3}{7}+\dfrac{1}{7}\right)-\dfrac{2}{17}\cdot\dfrac{8}{13}\)

\(=\dfrac{5}{13}\cdot\dfrac{-2}{7}-\dfrac{2}{17}\cdot\dfrac{8}{13}\)

\(=\dfrac{-10}{91}-\dfrac{16}{221}\)

\(=\dfrac{-282}{1547}\)

\(\dfrac{-5}{13}.\dfrac{3}{7}-\dfrac{2}{17}.\dfrac{8}{13}+\dfrac{5}{13}.\dfrac{1}{7}\) 

\(=\dfrac{5}{13}.\dfrac{-3}{7}-\dfrac{2}{17}.\dfrac{8}{13}+\dfrac{5}{13}.\dfrac{1}{7}\)

\(=\dfrac{5}{13}.\left(\dfrac{-3}{7}+\dfrac{1}{7}\right)+\dfrac{-2}{17}.\dfrac{8}{13}\) 

\(=\dfrac{5}{13}.\dfrac{-2}{7}+\dfrac{-2}{13}.\dfrac{8}{17}\)

\(=\dfrac{-2}{13}.\dfrac{5}{7}+\dfrac{-2}{13}.\dfrac{8}{17}\) 

\(=\dfrac{-2}{13}.\left(\dfrac{5}{7}+\dfrac{8}{17}\right)\) 

\(=\dfrac{-2}{13}.\dfrac{141}{119}\) 

\(=\dfrac{-282}{1547}\)

18 x 19 x 20 x 21 x 22 = 252y0640

Vì 18 có thể bằng 9 x 2 vậy 252y0640 phải chia hết cho 9

Muốn chia hết cho 9 thì tổng của 252y0640 phải có tổng các cs là 27 mà : 2 + 5 + 2 + 0 + 6 + 4 + 0 = 19

Thì y = 27 - 19 = 8

Ai kết bn ko!

Tiện thể tk luôn nha!

KONOSUBA

số a = 8

số y = 8

vì 18*19*20*21*22*8 =25280640

\(A=\frac{3}{4}-\left(\frac{5}{2}+\frac{5}{3}\right)+\left(\frac{-1}{3}\right)^2\)

\(\Rightarrow A=\frac{3}{4}-\left(\frac{15}{6}+\frac{10}{6}\right)+\frac{1}{9}\)

\(\Rightarrow A=\frac{3}{4}-\frac{25}{6}+\frac{1}{9}\)

\(\Rightarrow A=\frac{18}{24}-\frac{100}{24}+\frac{1}{9}\)

\(\Rightarrow A=\frac{-82}{24}+\frac{1}{9}\)

\(\Rightarrow A=\frac{-41}{12}+\frac{1}{9}=\frac{-123}{36}+\frac{4}{36}=\frac{-119}{36}\)

Vậy A=\(\frac{-119}{36}\)

b)\(B=\frac{-11}{19}.\frac{4}{13}+\frac{-11}{13}.\frac{15}{19}+\frac{11}{13}\)

\(\Rightarrow B=\frac{-11}{19}.\frac{4}{13}+\frac{11}{13}.\left(\frac{-15}{19}+1\right)\)

\(\Rightarrow B=\frac{-11}{19}.\frac{4}{13}+\frac{11}{13}.\frac{4}{19}\)

\(\Rightarrow B=\frac{-11}{13}.\frac{4}{19}+\frac{11}{13}.\frac{4}{19}=\frac{4}{19}.\left(\frac{-11}{13}+\frac{11}{13}\right)=\frac{4}{19}.\frac{0}{13}=\frac{4}{19}.0=0\)

Vậy B=0

Chúc bn học tốt

12/17 : 4 = 3/17

12 : 6/13 = 26

9 : 3/5 x 4/15 = 4

72 : 45 = 1,6

281,6 : 8 = 35,2

300,72 : 53,7 = 5,6

a) 3/7

b) 26

c) 8/5

d) 176/5

e) 28/5

\(\frac{12}{17}\): 4 = \(\frac{3}{17}\)

12 : \(\frac{6}{13}\)=26

9 : \(\frac{3}{5}\)x \(\frac{4}{15}\)=4

72 : 45 = 1,6

281,6 : 8 = 35,2

300,72 : 53,7 = 5,6

Tham khảo:Câu hỏi của Aresec Ruby - Toán lớp 6 - Học trực tuyến OLM

a) 35 . 23 + 35 . 41 + 64 . 65

= 35 . ( 23 + 41) + 64 . 65

= 35 . 64 + 64 . 65

= ( 35 + 65 ) . 64

= 100 . 64

= 6400

b) 29 . 87 - 29 . 23 + 64 . 71

= 29 . (87 - 23) + 64 .71

= 29 . 64 + 64 . 71

= (29 + 71) . 64

= 100 . 64

= 6400

*Dấu chấm trên bài là dấu nhân nha*

Alo 98 %của 7

tinh bang cach thuan tien nhat

113 x 3 x 18 = 6102

= 6x3x113^3

= 18x113^3

= 25972146

\(=\dfrac{1}{2}\cdot\dfrac{2}{3}\cdot...\cdot\dfrac{7}{8}=\dfrac{1}{8}\)

`= 1/2 xx 2/3 xx...xx 7/8`

`= 1/8`

\(=\dfrac{1}{2}\times\dfrac{2}{3}\times\dfrac{3}{4}\times...\times\dfrac{6}{7}\times\dfrac{7}{8}\\ =\dfrac{1}{8}\)