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18 tháng 10 2020

\(\left(\frac{1}{3}+\frac{12}{67}+\frac{13}{41}\right)-\left(\frac{79}{67}-\frac{28}{41}\right)\)

=\(\frac{1}{3}+\frac{12}{67}+\frac{13}{41}-\frac{79}{67}+\frac{28}{41}\)

\(=\frac{1}{3}+\left(\frac{12}{67}-\frac{79}{67}\right)+\left(\frac{13}{41}+\frac{28}{41}\right)\)

\(=\frac{1}{3}-1+1\)

\(=\frac{1}{3}\)

24 tháng 12 2022

\(\left(\dfrac{1}{3}+\dfrac{12}{67}+\dfrac{13}{41}\right)-\left(\dfrac{79}{67}-\dfrac{28}{41}\right)\)
\(=\dfrac{1}{3}+\dfrac{12}{67}+\dfrac{13}{41}-\dfrac{79}{67}+\dfrac{28}{41}\)
\(=\dfrac{1}{3}+\left(\dfrac{12}{67}-\dfrac{79}{67}\right)+\left(\dfrac{13}{41}+\dfrac{28}{41}\right)\)
\(=\dfrac{1}{3}+\left(-1\right)+1=\dfrac{1}{3}+0=\dfrac{1}{3}\)
\(\left(\dfrac{15}{4}-5x\right).\left(9x^2-4\right)=0\)
\(\left[{}\begin{matrix}\dfrac{15}{4}-5x=0\\9x^2-4=0\end{matrix}\right.\)
\(\left[{}\begin{matrix}5x=\dfrac{15}{4}\\9x^2=4\end{matrix}\right.\)
\(\left[{}\begin{matrix}x=\dfrac{3}{4}\\x=\dfrac{2}{3}\end{matrix}\right.\)

24 tháng 10 2021

1: \(\dfrac{4}{23}+\dfrac{5}{21}+\dfrac{1}{2}-\dfrac{4}{23}+\dfrac{16}{21}\)

\(=1+\dfrac{1}{2}\)

\(=\dfrac{3}{2}\)

2: \(\left(\dfrac{1}{3}+\dfrac{12}{67}+\dfrac{13}{41}\right)-\left(\dfrac{79}{67}-\dfrac{28}{41}\right)\)

\(=\dfrac{1}{3}+\dfrac{12}{67}+\dfrac{13}{41}-\dfrac{79}{67}+\dfrac{28}{41}\)

\(=\dfrac{1}{3}\)

\(=\left(25+\dfrac{12}{67}+9+\dfrac{13}{41}-8-\dfrac{12}{67}+3+\dfrac{28}{41}\right)\cdot\dfrac{-21}{13}\)

\(=\left(25+9-8+3+1\right)\cdot\dfrac{-21}{13}=\dfrac{-630}{13}\)

4 tháng 8 2018

Ta có : a, 25/7 + 13/21 - 11/7 + 17/21 + 1/3 .

= ( 25/7 - 11/7 ) + ( 13/21 + 17/21 + 1/3 ) .

= 2 + ( 20/21 + 7/21 ) .

= 2 + 9/7 .

= 23/7 .

b, ( 1/3 + 12/67 + 13/41 ) - ( 79/67 - 28/41 ) .

= 1/3 + 12/67 + 13/41 - 79/67 + 28/41 .

= 1/3 + ( 12/67 - 79/67 ) + ( 13/41 + 28/41 ) .

= 1/3 - 1 + 1 .

= 1/3 .

c, ( 11/4 . -5/9 - 4/9 . 11/4 ) . 8/33 .

= [ 11/4 . ( -5/9 - 4/9 ) ] . 8/33 .

= [ 11/4 . ( - 1 ) ] . 8/33 .

= -11/4 . 8/33 .

= -2/3 .

d, 38/45 - ( 8/45 - 17/51 - 3/11 ) .

= 38/45 - 8/45 + 17/51 + 3/11 .

= 2/3 + 17/51 + 3/11 .

= 374/561 + 187/561 + 153/561 .

= 14/11 .

14 tháng 9 2021

a. \(\dfrac{-2}{3}+\dfrac{-1}{5}+\dfrac{3}{4}-\dfrac{5}{6}-\dfrac{7}{10}\)

\(\dfrac{-4}{6}+\dfrac{-2}{10}+\dfrac{3}{4}-\dfrac{5}{6}-\dfrac{7}{10}\)

\(\dfrac{-3}{2}+\dfrac{1}{2}+\dfrac{3}{4}\)

= (-1) + \(\dfrac{3}{4}\)

\(\dfrac{-4}{4}+\dfrac{3}{4}\)

\(\dfrac{-1}{4}\)

19 tháng 12 2018

\(a,=\left(\frac{15}{12}-\frac{3}{12}\right)+\left(\frac{5}{13}-\frac{18}{13}\right)\)

\(=1+-1\)

\(=0\)

5 tháng 7 2023

a) \(2\cdot31\cdot12+4\cdot6\cdot41+8\cdot28\cdot3\)

\(=24\cdot31+24\cdot41+24\cdot28\)

\(=24\cdot\left(31+41+28\right)\)

\(=24\cdot\left(72+28\right)\)

\(=24\cdot100\)

\(=2400\)

b) \(3,9\cdot\dfrac{13}{10}+\dfrac{0,87}{0,01}\cdot0,39\)

\(=\dfrac{3,9}{10}\cdot13+87\cdot0,39\)

\(=0,39\cdot13+87\cdot0,39\)

\(=0,39\cdot\left(13+87\right)\)

\(=0,39\cdot100\)

\(=39\)