a) 5 × 7 – 7 = 28

b) 3 × 9 – 18 = 9

c) 5 × 7 + 7 = 42

d) 4 × 6 – 18 = 6

a: \(\left(-\dfrac{5}{6}+\dfrac{2}{5}\right):\dfrac{3}{8}+\left(\dfrac{4}{5}-\dfrac{11}{30}\right):\dfrac{3}{8}\)

\(=\left(-\dfrac{5}{6}+\dfrac{2}{5}\right)\cdot\dfrac{8}{3}+\left(\dfrac{4}{5}-\dfrac{11}{30}\right)\cdot\dfrac{8}{3}\)

\(=\dfrac{8}{3}\left(-\dfrac{5}{6}+\dfrac{2}{5}+\dfrac{4}{5}-\dfrac{11}{30}\right)\)

\(=\dfrac{8}{3}\cdot\dfrac{-25+36-11}{30}\)

=0

b: \(\left(-\dfrac{3}{4}+\dfrac{2}{5}\right):\dfrac{3}{7}+\left(\dfrac{3}{5}+\dfrac{-1}{4}\right):\dfrac{3}{7}\)

\(=\left(-\dfrac{3}{4}+\dfrac{2}{5}\right)\cdot\dfrac{7}{3}+\left(\dfrac{3}{5}-\dfrac{1}{4}\right)\cdot\dfrac{7}{3}\)

\(=\dfrac{7}{3}\left(-\dfrac{3}{4}+\dfrac{2}{5}+\dfrac{3}{5}-\dfrac{1}{4}\right)\)

\(=\dfrac{7}{3}\cdot0=0\)

c: \(\dfrac{-13}{18}\cdot\dfrac{5}{8}+\dfrac{-5}{18}\cdot\dfrac{2}{9}+\dfrac{-13}{18}\cdot\dfrac{3}{8}+\dfrac{-5}{18}\cdot\dfrac{7}{9}\)

\(=\left(-\dfrac{13}{18}\cdot\dfrac{5}{8}+\dfrac{-13}{18}\cdot\dfrac{3}{8}\right)+\left(-\dfrac{5}{18}\cdot\dfrac{2}{9}+\dfrac{-5}{18}\cdot\dfrac{7}{9}\right)\)

\(=-\dfrac{13}{18}\left(\dfrac{5}{8}+\dfrac{3}{8}\right)+\dfrac{-5}{18}\left(\dfrac{2}{9}+\dfrac{7}{9}\right)\)

\(=-\dfrac{13}{18}-\dfrac{5}{18}=-\dfrac{18}{18}=-1\)

d: Sửa đề: \(\dfrac{-11}{19}\cdot\dfrac{4}{9}+\dfrac{-8}{19}\cdot\dfrac{3}{7}+\dfrac{-11}{19}\cdot\dfrac{5}{9}+\dfrac{-8}{19}\cdot\dfrac{4}{7}\)

\(=\left(-\dfrac{11}{19}\cdot\dfrac{4}{9}+\dfrac{-11}{19}\cdot\dfrac{5}{9}\right)+\left(\dfrac{-8}{19}\cdot\dfrac{3}{7}+\dfrac{-8}{19}\cdot\dfrac{4}{7}\right)\)

\(=-\dfrac{11}{19}\left(\dfrac{4}{9}+\dfrac{5}{9}\right)+\dfrac{-8}{19}\left(\dfrac{3}{7}+\dfrac{4}{7}\right)\)

\(=-\dfrac{11}{19}-\dfrac{8}{19}=-\dfrac{19}{19}=-1\)

\(a.\left(-\dfrac{5}{6}+\dfrac{2}{5}\right):\dfrac{3}{8}+\left(\dfrac{4}{5}-\dfrac{11}{30}\right):\dfrac{3}{8}\)

\(=\left(-\dfrac{13}{30}\right):\dfrac{3}{8}+\dfrac{13}{30}:\dfrac{3}{8}\)

\(=\left[\left(-\dfrac{13}{30}+\dfrac{13}{30}\right)\right]:\dfrac{3}{8}\)

\(=0:\dfrac{3}{8}=0\)

\(b.\left(-\dfrac{3}{4}+\dfrac{2}{5}\right):\dfrac{3}{7}+\left(\dfrac{3}{5}+-\dfrac{1}{4}\right):\dfrac{3}{7}\)

\(=\left(-\dfrac{7}{20}\right):\dfrac{3}{7}+\dfrac{7}{20}:\dfrac{3}{7}\)

\(=\left[\left(-\dfrac{7}{20}+\dfrac{7}{20}\right)\right]:\dfrac{3}{7}=0:\dfrac{3}{7}=0\)

\(c.-\dfrac{13}{18}.\dfrac{5}{8}+-\dfrac{5}{18}.\dfrac{2}{9}+-\dfrac{13}{18}.\dfrac{3}{8}+-\dfrac{5}{18}.\dfrac{7}{9}\)

\(=\left(\dfrac{5}{8}+\dfrac{3}{8}\right).-\dfrac{13}{18}+\left(\dfrac{2}{9}+\dfrac{7}{9}\right).-\dfrac{5}{18}\)

\(=1.-\dfrac{13}{18}+1.-\dfrac{5}{18}=-\dfrac{13}{18}+-\dfrac{5}{18}=-1\)

\(d.-\dfrac{11}{19}.\dfrac{4}{9}+\dfrac{-8}{19}.\dfrac{3}{7}+-\dfrac{11}{19}.\dfrac{5}{9}+-\dfrac{9}{19}.\dfrac{4}{7}\)

\(=\left(\dfrac{4}{9}+\dfrac{5}{9}\right).-\dfrac{11}{19}+-\dfrac{24}{133}+-\dfrac{36}{133}\)

\(=-\dfrac{11}{19}+-\dfrac{60}{133}=-\dfrac{137}{133}\)

a, (\(\dfrac{9}{4}\))⁵ : (\(\dfrac{1}{4}\))⁵

= (\(\dfrac{9}{4}\) : \(\dfrac{1}{4}\))⁵

= 9⁵ 

= 59049

b, 18² : 9²

= (18:9)²

= 2²

= 4

c, [(-2)\(^4\)]³ 

= 2¹²

= 4096

d, 5⁷.(\(\dfrac{1}{5}\))⁷

= (5.\(\dfrac{1}{5}\))⁷

= 1⁷

= 1

e, (6,5)³: (6,5)²

= 6,5

mn giúp mình nha mình cần đáp án ngay bây giờ

câu a bằng 15/8

câu b bằng 19/6

câu c bằng 3/10

câu d bằng 27/4

a) MSC của 4; 8 và 12 là 24 = \(\dfrac{66}{24}-\dfrac{27}{24}+\dfrac{30}{24}\) =\(\dfrac{69}{24}\) = \(\dfrac{23}{8}\) b) = \(\dfrac{126}{84}\)+\(\dfrac{5}{3}\) =\(\dfrac{3}{2}+\dfrac{5}{3}\) Quy đồng hai p/s ta có: =\(\dfrac{9}{6}+\dfrac{10}{6}\) = \(\dfrac{19}{6}\) c) = \(\dfrac{13}{18}\)x \(\dfrac{9}{5}+1\)

= \(\dfrac{117}{90}+1\) =\(\dfrac{207}{90}\) =\(\dfrac{23}{10}\) d) =3+ \(\dfrac{9}{4}\)x\(\dfrac{5}{3}\) =3+\(\dfrac{45}{12}\) =3+\(\dfrac{15}{4}\) =\(\dfrac{27}{4}\)

`a: =(7/3-4/3)+11/5=16/5`

`b: =(18/13-5/13)+55/46=1+55/46=101/46`

`c: =27/25-4/9-2/25+5/9=(27/25-2/25)+(5/9-4/9)=1+1/9=10/9`

a)\(\frac{-5}{18}+\frac{32}{45}-\frac{9}{10}\)

\(=\frac{-25}{90}+\frac{64}{90}-\frac{81}{90}\)

\(=-\frac{42}{90}=-\frac{7}{15}\)

b)\(\frac{3}{4}-\left(-\frac{5}{8}\right)+\frac{9}{4}-\frac{3}{16}\)

\(=\frac{3}{4}+\frac{5}{8}+\frac{9}{4}-\frac{3}{16}\)

\(=\frac{12}{16}+\frac{10}{16}+\frac{36}{16}-\frac{3}{16}\)

\(=\frac{58}{16}=\frac{29}{8}\)

c) \(\frac{11}{125}-\frac{17}{18}-\frac{5}{7}+\frac{4}{9}+\frac{17}{14}=\frac{11}{125}\)

d) \(\frac{-2}{5}-\frac{3}{10}-\left(-\frac{1}{2}\right)\)

\(=-\frac{2}{5}-\frac{3}{10}+\frac{1}{2}\)

\(=-\frac{4}{10}-\frac{3}{10}+\frac{5}{10}\)

\(=-\frac{2}{10}=-\frac{1}{5}\)

a) chứng tỏ : abcabc chia hết cho 11

Ta có 123123:11=11193

Vậy abcabc chia hết cho 11

b)\(\frac{9\cdot15\cdot21\cdot12\cdot20}{5\cdot6\cdot45\cdot18\cdot4}=\frac{9\cdot3\cdot5\cdot3\cdot7\cdot2\cdot2\cdot3\cdot2\cdot2\cdot5}{5\cdot2\cdot3\cdot5\cdot3\cdot3\cdot2\cdot3\cdot3\cdot2\cdot2}\)\(=\frac{7\cdot5}{3}=\frac{35}{3}\)

Ghi đầy đủ nha

bn có thể ghi rõ ràng đc ko?

a)\(-\dfrac{3}{7}+\dfrac{5}{13}+\dfrac{3}{7}\) 

=\(\left(-\dfrac{3}{7}+\dfrac{3}{7}\right)+\dfrac{5}{13}\) 

=\(0+\dfrac{5}{13}\) 

=\(\dfrac{5}{13}\)

A) 3/7 + 4/9 + 4/7 + 5/9 = ( 4/9+5/9) + ( 3/7 + 4/7) = 1+ 1 = 2         

B) 1/5 + 4/11 + 4/5 + 7/11 = ( 4/11 + 7/11) + ( 1/5 + 4/5) = 1+1=2         

C) 1/15 + 4/15 + 5/18 + 7/18= ( 1/15+4/15) + (5/18+7/15)= 5/15 + 12/15 = 17/15         

D) 1/8 + 1/12 + 3/8 + 5/12 = (1/8 + 3/8) + ( 1/12 + 1/12) = 4/8 + 2/12 = 64/96

K nha

18 : 9 = 2

27 : 9 = 3

36 : 9 = 4

45 : 9 = 5

18 : 2 = 9

27 : 3 = 9

36 : 4 = 9

45 : 5 = 9