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17 tháng 3

\(\dfrac{-25}{5-x}=\dfrac{5-x}{-16}\)

\(\Rightarrow\dfrac{-25}{-\left(x-5\right)}=\dfrac{-\left(x-5\right)}{-16}\)

\(\Rightarrow\dfrac{25}{x-5}=\dfrac{x-5}{16}\)

\(\Rightarrow\left(x-5\right)^2=25\cdot16\)

\(\Rightarrow\left(x-5\right)^2=400\)

\(\Rightarrow\left(x-5\right)^2=20^2\)

TH1: \(x-5=20\)

\(\Rightarrow x=25\)

TH2: \(x-5=-20\)

\(\Rightarrow x=-15\)

Vậy: ... 

12 tháng 3 2022

a) \(\dfrac{7}{9}\times\dfrac{13}{25}\times\dfrac{9}{7}=\left(\dfrac{7}{9}\times\dfrac{9}{7}\right)\times\dfrac{13}{25}=1\times\dfrac{13}{25}=\dfrac{13}{25}\)

b) \(\dfrac{5}{9}\times\dfrac{21}{25}+\dfrac{21}{25}\times\dfrac{4}{9}\)

\(=\dfrac{21}{25}\times\left(\dfrac{5}{9}+\dfrac{4}{9}\right)\)

\(=\dfrac{21}{25}\times1=\dfrac{21}{25}\)

c) \(\dfrac{19}{5}\times\dfrac{11}{16}-\dfrac{9}{5}\times\dfrac{11}{16}\)

\(=\dfrac{11}{16}\times\left(\dfrac{19}{5}-\dfrac{9}{5}\right)\)

\(=\dfrac{11}{16}\times2=\dfrac{22}{16}=\dfrac{11}{8}\)

 

21 tháng 9 2016

\(5\left(x-3\right)=25\)

\(x-3=25:5=5\)

\(x=5+3=8\)

\(x-3=5=5x=8\)

Hình như sai đề

\(10+2x=16\)

\(2x=6\)

\(x=3\)

mik còn k pit bn hỏi cái dj

21 tháng 9 2016
trong sbt
22 tháng 6 2016

Câu 1 sai đề r nhé

22 tháng 6 2016

Phải là:(2x-5)^2=x(2x-5)

26 tháng 3 2022

1)

2/5x3/4+3/4x3/5

= 3/10+9/20

=6/20+9/20

=3/4

26 tháng 3 2022

2)

= 41/50-8/25

=41/50-16/50

=1/2

3)

=4/3-10/9

=12/9-10/9

=2/9

 

12 tháng 2 2018

\(5-x=17-\left(-5\right)\)

\(5-x=22\)

\(x=5-22\)

\(x=-17\)

a/ 5 - x = 17 - (-5) 

5-x = 22

x= -17

1) Ta có: \(\left(-\dfrac{2}{3}\right)^2\cdot\dfrac{-9}{8}-25\%\cdot\dfrac{-16}{5}\)

\(=\dfrac{4}{9}\cdot\dfrac{-9}{8}-\dfrac{1}{4}\cdot\dfrac{-16}{5}\)

\(=\dfrac{-1}{2}+\dfrac{4}{5}\)

\(=\dfrac{-5}{10}+\dfrac{8}{10}=\dfrac{3}{10}\)

2) Ta có: \(-1\dfrac{2}{5}\cdot75\%+\dfrac{-7}{5}\cdot25\%\)

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

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

3) Ta có: \(-2\dfrac{3}{7}\cdot\left(-125\%\right)+\dfrac{-17}{7}\cdot25\%\)

\(=\dfrac{-17}{7}\cdot\dfrac{-5}{4}+\dfrac{-17}{7}\cdot\dfrac{1}{4}\)

\(=\dfrac{-17}{7}\cdot\left(\dfrac{-5}{4}+\dfrac{1}{4}\right)\)

\(=\dfrac{17}{7}\)

4) Ta có: \(\left(-2\right)^3\cdot\left(\dfrac{3}{4}\cdot0.25\right):\left(2\dfrac{1}{4}-1\dfrac{1}{6}\right)\)

\(=\left(-8\right)\cdot\left(\dfrac{3}{4}\cdot\dfrac{1}{4}\right):\left(\dfrac{9}{4}-\dfrac{7}{6}\right)\)

\(=\left(-8\right)\cdot\dfrac{3}{16}:\dfrac{54-28}{24}\)

\(=\dfrac{-3}{2}\cdot\dfrac{24}{26}\)

\(=\dfrac{-72}{52}=\dfrac{-18}{13}\)

9 tháng 3 2023

\(\dfrac{7}{16}+\dfrac{-1}{8}+\dfrac{9}{32}=\dfrac{14}{32}-\dfrac{4}{32}+\dfrac{9}{32}=\dfrac{19}{32}\)

\(\dfrac{5}{4}-\dfrac{25}{30}\times\dfrac{37}{44}+\dfrac{-25}{30}\times\dfrac{13}{44}+\dfrac{-25}{30}\times\dfrac{-6}{44}\)

\(=-\dfrac{25}{30}\times\left(\dfrac{5}{4}+\dfrac{37}{44}+\dfrac{13}{44}-\dfrac{6}{44}\right)\)

\(=-\dfrac{25}{30}\times\left(\dfrac{55}{44}+\dfrac{37}{44}+\dfrac{13}{44}-\dfrac{6}{44}\right)\)

\(=-\dfrac{25}{30}\times\dfrac{99}{44}\)

\(=-\dfrac{5}{6}\times\dfrac{9}{4}\)

\(=-\dfrac{15}{8}\)

9 tháng 3 2023

\(\left(\dfrac{7}{16}+\dfrac{-1}{8}+\dfrac{9}{32}\right):\dfrac{5}{4}\)

\(=\left(\dfrac{14}{32}+\dfrac{-4}{32}+\dfrac{9}{32}\right):\dfrac{5}{4}\)

\(=\dfrac{19}{32}:\dfrac{5}{4}\)

\(=\dfrac{19}{32}.\dfrac{4}{5}=\dfrac{19.4}{32.5}=\dfrac{19}{40}\)

\(\dfrac{-25}{30}.\dfrac{37}{44}+\dfrac{-25}{30}.\dfrac{13}{44}+\dfrac{-25}{30}.\dfrac{-6}{44}\)

\(=\dfrac{-25}{30}.\left(\dfrac{37}{44}+\dfrac{13}{44}+\dfrac{-6}{44}\right)\)

\(=\dfrac{-25}{30}.\dfrac{44}{44}=\dfrac{-5}{6}.1=-\dfrac{5}{6}\)

 

 

15 tháng 4 2019

a, \(\left(\frac{4}{9}.\frac{3}{7}\right).\frac{7}{4}=\frac{4}{9}\left(\frac{3}{7}.\frac{7}{4}\right)=\frac{4}{9}.\frac{3}{4}=\frac{3}{9}=\frac{1}{3}\)

b, \(\left(\frac{6}{5}.\frac{4}{5}\right).\frac{25}{16}=\frac{6}{5}\left(\frac{4}{5}.\frac{25}{16}\right)=\frac{6}{5}.\frac{5}{4}=\frac{6}{4}=\frac{3}{2}\)

c, \(\left(\frac{7}{8}.\frac{16}{9}\right).\frac{3}{14}=\frac{7}{8}\left(\frac{16}{9}.\frac{3}{14}\right)=\frac{7}{8}.\frac{8}{21}=\frac{7}{21}=\frac{1}{3}\)

22 tháng 3 2022

a, (49.37).74=49(37.74)=49.34=39=13

b, (65.45).2516=65(45.2516)=65.54=64=32

c, (78.169).314=78(169.314)=78.821=721=13

 Nếu đúng thì k cho mình nhé bạn!
14 tháng 4 2019

( 4/9 x 3/7 ) x 7/4 = 4/9 x ( 3/7 x 7/4 ) =4/9 x 21/28 = 84/252

( 6/5 x 4/5 ) x 25/16 = ( 25/16 x 4/5 ) x 6/5 = 100/80 x 6/5 = 600/400