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11 tháng 7 2017
\(a.-8:\left(4\dfrac{1}{5}x+\dfrac{3}{10}\right)=4\dfrac{4}{9}\)
\(4\dfrac{1}{5}x+\dfrac{3}{10}=\left(-8\right):4\dfrac{4}{9}\)
\(4\dfrac{1}{5}x+\dfrac{3}{10}=\dfrac{-9}{5}\)
\(4\dfrac{1}{5}x=\dfrac{-9}{5}-\dfrac{3}{10}\)
\(4\dfrac{1}{5}x=\dfrac{-21}{10}\)
\(x=\dfrac{-21}{10}:\dfrac{21}{5}\)
\(x=\dfrac{-1}{2}\)
Vay \(x=\dfrac{-1}{2}\).
\(b.4\dfrac{2}{3}-\left(\dfrac{3}{5}:x\right)=-20\%\)
\(\dfrac{14}{3}-\left(\dfrac{3}{5}:x\right)=\dfrac{-1}{5}\)
\(\dfrac{3}{5}:x=\dfrac{14}{3}-\dfrac{-1}{5}\)
\(\dfrac{3}{5}:x=\dfrac{73}{15}\)
\(x=\dfrac{3}{5}:\dfrac{73}{15}\)
\(x=\dfrac{9}{73}\)
Vay \(x=\dfrac{9}{73}\).
Câu c; d; e tương tự nhé.
16 tháng 4 2017
Câu 1:
Ta có: \(\dfrac{x-4}{y-3}=\dfrac{4}{3}\)
=> \(3.\left(x-4\right)=4.\left(y-3\right)\)
=>\(3x-12=4y-12\)
=>\(3x=4y\) (1)
Ta có: \(x-y=5\)
=> \(y=y+5\) Thay vào (1) ta có:
\(3.\left(y+5\right)=4.\)y
=>\(3y+15=4y\)
=> \(15=4y-3y\)
=> 15 = y
=> y =15
ta có: x = y +5
=> x = 15 +5
=> x =20
16 tháng 4 2017
Câu 2:
\(B=\dfrac{10}{56}+\dfrac{10}{140}+\dfrac{10}{260}+...+\dfrac{10}{1400}\)
\(B=\dfrac{5}{28}+\dfrac{6}{70}+\dfrac{5}{130}+...+\dfrac{5}{700}\)
\(B=\dfrac{5}{4.7}+\dfrac{5}{7.10}+\dfrac{5}{10.13}+...+\dfrac{5}{25.28}\)
\(B=5,\left(\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{13}+...+\dfrac{1}{25}-\dfrac{1}{28}\right)\)
\(3B=5.\left(\dfrac{3}{4.7}+\dfrac{3}{7.10}+\dfrac{3}{10.13}+...+\dfrac{3}{25.28}\right)\)
\(3B=5.\left(\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{13}+...+\dfrac{1}{25}-\dfrac{1}{28}\right)\)
\(3B=5.\left(\dfrac{1}{4}-\dfrac{1}{28}\right)\)
\(3B=5.\dfrac{3}{14}\)
\(B=\dfrac{15}{14}:3=\dfrac{5}{14}\)
Câu 3:
38 - (|x+10|+13) = \(\left(-6\right)^{20}:\left(9^9.4^{10}\right)\)
=> \(38-\left(\left|x+10\right|+13\right)=\left(2.3\right)_{ }^{20}:\)\(\left[\left(3^2\right)^9.\left(2^2\right)^4\right]\)
=>\(38-\left(\left|x+10\right|+13\right)=2^{20}.3^{20}:\left(3^{18}.2^{20}\right)\)
=> \(38-\left(\left|x+10\right|+13\right)=\dfrac{3^{20}.2^{20}}{3^{18}.2^{20}}\)
=> \(38-\left(\left|x+10\right|+13\right)=9\)
=> |x +10| + 13 = 38 -9
=> |x+10| +13 = 29
=> |x+10| = 29 -13
=> |x+10| = 16
\(\Rightarrow\left[{}\begin{matrix}x+10=16\\x+10=-16\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=6\\x=-26\end{matrix}\right.\)
25 tháng 3 2017
Câu 1:
a,\(x=\dfrac{1}{4}+\dfrac{2}{13}\)
\(x=\dfrac{13}{52}+\dfrac{8}{52}=\dfrac{21}{52}\)
Câu 2:
a,\(\dfrac{-2}{5}+\dfrac{3}{-4}+\dfrac{6}{7}+\dfrac{3}{4}+\dfrac{2}{5}\)
\(=\left(\dfrac{-2}{5}+\dfrac{2}{5}\right)+\left(\dfrac{3}{-4}+\dfrac{3}{4}\right)+\dfrac{6}{7}\)
=\(0+0+\dfrac{6}{7}=\dfrac{6}{7}\)
b,\(\dfrac{7}{15}+\dfrac{4}{-9}+\dfrac{-2}{11}+\dfrac{8}{15}+\dfrac{-5}{9}\)
=\(\left(\dfrac{7}{15}+\dfrac{8}{15}\right)+\left(\dfrac{4}{-9}+\dfrac{-5}{9}\right)+\dfrac{-2}{11}\)
=\(\dfrac{15}{15}+\dfrac{-9}{9}+\dfrac{-2}{11}=1+\left(-1\right)+\dfrac{-2}{11}\)
=\(0+\dfrac{-2}{11}=\dfrac{-2}{11}\)
c, \(\dfrac{-5}{7}+\dfrac{5}{13}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)
=\(\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+\dfrac{-5}{7}\)
=\(\dfrac{13}{13}+\dfrac{-41}{41}+\dfrac{-5}{7}=1+\left(-1\right)+\dfrac{-5}{7}\)
=\(0+\dfrac{-5}{7}=\dfrac{-5}{7}\)
21 tháng 4 2017
tìm x a)
\(\dfrac{7}{2}\)-\(\left(x+\dfrac{7}{10}\right)\): \(\dfrac{6}{5}\) = \(\dfrac{-5}{4}\)
\(\left(x+\dfrac{7}{10}\right)\): \(\dfrac{6}{5}\) = \(\dfrac{-5}{4}\) + \(\dfrac{7}{2}\)
\(\left(x+\dfrac{7}{10}\right)\): \(\dfrac{6}{5}\) = \(\dfrac{-5}{12}+\dfrac{7}{12}\)
\(\left(x+\dfrac{7}{10}\right)\): \(\dfrac{6}{5}\) = \(\dfrac{-12}{12}=1\)
\(x+\dfrac{7}{10}\)= 1 . \(\dfrac{6}{5}\)
*Rồi tự làm phần tt đi
2 tháng 3 2018
\(a.\dfrac{3}{5}-\dfrac{-7}{10}-\dfrac{13}{-20}=\dfrac{12}{20}-\dfrac{-14}{20}-\dfrac{-13}{20}=\dfrac{12-\left(-14\right)-\left(-13\right)}{20}=\dfrac{39}{20}\)
\(b.\dfrac{3}{4}+\dfrac{-1}{3}-\dfrac{5}{18}=\dfrac{3}{4}+\left(\dfrac{-6}{18}-\dfrac{5}{18}\right)=\dfrac{3}{4}+\dfrac{-11}{18}=\dfrac{27}{36}-\dfrac{-22}{36}=\dfrac{49}{36}\)
\(c.\dfrac{3}{13}-\dfrac{5}{-8}+\dfrac{-1}{2}=\dfrac{3}{13}-\left(\dfrac{5}{-8}+\dfrac{-4}{8}\right)=\dfrac{3}{13}-\dfrac{1}{8}=\dfrac{24}{104}-\dfrac{13}{104}=\dfrac{11}{104}\)
\(d.\dfrac{1}{2}+\dfrac{1}{-3}=\dfrac{3}{6}+\dfrac{-2}{6}=\dfrac{1}{6}\)
VA
2 tháng 3 2018
\(a,\dfrac{3}{5}-\dfrac{-7}{10}-\dfrac{13}{-20}\)
\(=\dfrac{12}{20}+\dfrac{14}{20}+\dfrac{13}{20}\)
\(=\dfrac{12+14+13}{20}\)
\(=\dfrac{39}{20}\)
\(b,\dfrac{3}{4}+\dfrac{-1}{3}-\dfrac{5}{18}\)
\(=\dfrac{27}{36}+\dfrac{-12}{36}-\dfrac{10}{36}\)
\(=\dfrac{27+\left(-12\right)-10}{36}\)
\(=\dfrac{5}{36}\)
\(c,\dfrac{3}{13}-\dfrac{5}{-8}+\dfrac{-1}{2}\)
\(=\dfrac{24}{104}-\dfrac{-65}{104}+\dfrac{-52}{104}\)
\(=\dfrac{24-\left(-65\right)+\left(-52\right)}{104}\)
\(=\dfrac{37}{104}\)
\(d,\dfrac{1}{2}+\dfrac{1}{-3}\)
\(=\dfrac{3}{6}+\dfrac{-2}{6}\)
\(=\dfrac{3+\left(-2\right)}{6}\)
\(=\dfrac{1}{6}\)
DH
21 tháng 6 2017
a, \(\left(2\dfrac{3}{5}-3\dfrac{5}{9}\right):\left(3\dfrac{10}{21}-1\dfrac{3}{7}\right)\)
\(=\dfrac{-43}{45}:\dfrac{43}{21}=\dfrac{-43}{45}.\dfrac{21}{43}=\dfrac{-7}{15}\)
b, \(5\dfrac{1}{2}-14\dfrac{3}{7}:\dfrac{9}{13}-3\dfrac{4}{7}:\dfrac{9}{13}\)
\(=5\dfrac{1}{2}-14\dfrac{3}{7}.\dfrac{13}{9}-3\dfrac{4}{7}.\dfrac{13}{9}\)
\(=5\dfrac{1}{2}-\dfrac{13}{9}.\left(14\dfrac{3}{7}+\dfrac{4}{7}\right)\)
\(=5\dfrac{1}{2}-\dfrac{13}{9}.15=5\dfrac{1}{2}-\dfrac{65}{3}\)
\(=\dfrac{-97}{6}\)
Chúc bạn học tốt!!!
WT
8 tháng 3 2017
mình ghi nhầm nên các bạn cứ hết hai phân số là một câu nhé ví dụ như \(\dfrac{-5}{8}\):\(\dfrac{15}{4}\)
26 tháng 6 2022
a: \(=\dfrac{1}{3}-\dfrac{6}{13}\cdot\dfrac{13}{36}\cdot\dfrac{9}{10}\)
\(=\dfrac{1}{3}-\dfrac{1}{6}\cdot\dfrac{9}{10}\)
\(=\dfrac{1}{3}-\dfrac{3}{20}=\dfrac{20-9}{60}=\dfrac{11}{60}\)
b: \(=\dfrac{1}{3}\cdot\dfrac{15}{7}\cdot\dfrac{34}{45}=\dfrac{15}{45}\cdot\dfrac{1}{3}\cdot\dfrac{34}{7}=\dfrac{34}{63}\)
15 tháng 5 2022
a: Đề sai rồi bạn
b: \(\dfrac{\left(1.16-x\right)\cdot5.25}{\left(10+\dfrac{5}{9}-7-\dfrac{1}{4}\right)\cdot\dfrac{36}{17}}=\dfrac{3}{4}\)
\(\Leftrightarrow21\left(1.16-x\right)=3\cdot\dfrac{36}{17}\cdot\left(3+\dfrac{5}{9}-\dfrac{1}{4}\right)\)
\(\Leftrightarrow21\left(1.16-x\right)=\dfrac{108}{17}\cdot\dfrac{108+20-9}{36}\)
\(\Leftrightarrow21\cdot\left(1.16-x\right)=21\)
=>1,16-x=1
hay x=0,16
Ta có: \(x-\dfrac{3}{13}+\dfrac{9}{20}-10\%\)
\(=x-\dfrac{60}{260}+\dfrac{117}{260}-\dfrac{26}{260}\)
\(=x+\dfrac{31}{260}\)