\(A=\frac{13}{28}\left(-\frac{5}{9}-\frac{4}{9}\right)=\frac{13}{28}\left(-\frac{9}{9}\right)=\frac{13}{28}\left(-1\right)\)

=> \(A=-\frac{13}{28}\)

A= -5/9x 13/28- 13/28x 4/9

  =13/28x (-5/9- 4/9)

  =13/28x (-1)

  =-13/28

Ta có: \(-\frac59\cdot\frac{13}{28}-\frac{13}{28}\cdot\frac49\)

\(=-\frac{13}{28}\left(\frac59+\frac49\right)\)

\(=-\frac{13}{28}\cdot\frac99=-\frac{13}{28}\)

-5/9 . 13/28 - 13/28 . 4/9

= 13/28 . (-5/9 - 4/9)

= 13/28 . (-1)

= -13/28

`-5/9 xx 13/28 - 13/28 xx 4/9`

`= 13/28 xx ((-5)/9 - 4/9)`

`= 13/28 xx (-1)`

`= -13/28`

\(\frac{-5}{9}.\frac{13}{28}-\frac{13}{28}.\frac{4}{9}\)

\(=\frac{13}{28}.\left(\frac{-5}{9}-\frac{4}{9}\right)\)

\(=\frac{13}{28}.\left(-1\right)\)

\(=\frac{-13}{28}\)

=13/28.(-5/9-4/9)

=13/28.(-1)

=-13/28

a, \(\left(31\frac{6}{13}+5\frac{9}{41}\right)-36\frac{6}{13}=31\frac{6}{16}+5\frac{9}{41}-36\frac{6}{13}\)

\(=\left(31\frac{6}{16}-31\frac{6}{16}\right)+5\frac{9}{41}\)

\(=0+5\frac{9}{41}=5\frac{9}{41}\)

b, \(\left(17\frac{29}{31}-3\frac{7}{8}\right)-\left(2\frac{28}{31}-4\right)=17\frac{9}{31}-3\frac{7}{8}-2\frac{28}{31}+4\)

\(\frac{-5}{9}.\frac{13}{28}-\frac{13}{28}.\frac{4}{9}\)

= \(\frac{13}{28}.\left(\frac{-5}{9}-\frac{4}{9}\right)\)

= \(\frac{13}{28}.\left(-1\right)=\frac{-13}{28}\)

~~~

#Sunrise

-13/28

\(\frac{-9}{56}< \frac{x}{7}< \frac{13}{-28}\Rightarrow\frac{-9}{56}< \frac{8x}{56}< \frac{-26}{56}\Rightarrow-9< 8x< -26\Rightarrow\)vô lí

vậy không tồn tại x

cảm ơn nhé bạn

1/ \(\frac{9.5^{20}.27^9-3.9^{15}.25^9}{7.3^{29}.125^6-3.3^9.15^{19}}\)

\(=\frac{5^{20}.3^{29}-3^{31}.5^{18}}{7.3^{29}.5^{18}-3^{29}.5^{19}}=\frac{3^{29}.5^{18}.\left(25-9\right)}{3^{29}.5^{18}.\left(7-5\right)}=\frac{16}{2}=8\)

CÁC BÀI CÒN LẠI TƯƠNG TỰ HẾT NHÉ E

a, A = ( 1/3 + 12/67 + 13/41 ) - ( 79/67 - 28/41 )

A = (\(\frac13\) + \(\frac{12}{67}\) + \(\frac{13}{41}\)) - (\(\frac{79}{67}\) - \(\frac{28}{41}\))

A = \(\frac13\) + \(\frac{12}{67}\) + \(\frac{13}{41}\) - \(\frac{79}{67}\) + \(\frac{28}{41}\)

A = - (\(\frac{79}{67}-\frac{12}{67}\)) + (\(\frac{13}{41}\) + \(\frac{28}{41}\))

A = - 1 + 1 + \(\frac13\)

A = 0 + \(\frac13\)

A = \(\frac13\)

b, B = 3/4×7 + 3/7×10 + 3/10×13 + ......+ 3/73×76

B = \(\frac{3}{4\times7}\) + \(\frac{3}{7\times10}\) + \(\frac{3}{10\times13}\) + ... + \(\frac{3}{73\times76}\)

B = \(\frac14-\frac17\) + \(\frac17-\frac{1}{10}\) + ... + \(\frac{1}{73}-\frac{1}{76}\)

B = \(\frac14\) - \(\frac{1}{76}\)

B = \(\frac{19}{76}-\) \(\frac{1}{76}\)

B = \(\frac{18}{76}\)

B = \(\frac{9}{38}\)