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2 tháng 4 2018
a)\(\left(\frac{3}{29}-\frac{1}{5}\right)\cdot\frac{29}{3}\)
\(=\left(\frac{3}{29}\cdot\frac{29}{3}\right)-\left(\frac{1}{5}\cdot\frac{29}{3}\right)\)
\(=1-\frac{29}{15}\)
\(=\frac{-14}{15}\)
b)\(\frac{16}{15}\cdot\frac{-5}{14}\cdot\frac{54}{24}\cdot\frac{56}{21}\)
=\(=\frac{16\cdot\left(-5\right)\cdot54\cdot56}{15\cdot14\cdot24\cdot21}\)
\(=\frac{2^4\cdot\left(-5\right)\cdot2\cdot3^3\cdot2^3\cdot7}{3\cdot5\cdot7\cdot2\cdot2^3\cdot3\cdot7}\)
\(=2^4\)
c)\(\frac{37}{7}\cdot\frac{8}{11}+\frac{37}{7}\cdot\frac{5}{11}-\frac{37}{7}\cdot\frac{2}{11}\)
\(=\frac{37}{7}\cdot\left(\frac{8}{11}+\frac{5}{11}-\frac{2}{11}\right)\)
\(=\frac{37}{7}\cdot1\)
\(=\frac{37}{7}\)
Đúng nhớ k nhen!
20 tháng 2 2017
a) \(-\frac{2x}{5}=\frac{-6}{3}\)
\(\Rightarrow-2x.3=-6.5\)
\(\Rightarrow-2x=\frac{-6.5}{3}\)
\(\Rightarrow-2x=-10\)
\(\Rightarrow x=\frac{-10}{-2}\)
\(\Rightarrow x=5\)
b) \(\frac{x-2}{18}=\frac{-1}{6}\)
\(\Rightarrow\left(x-2\right).6=-1.18\)
\(\Rightarrow x-2=\frac{-1.18}{6}\)
\(\Rightarrow x-2=-3\)
\(\Rightarrow x=-3+2\)
\(\Rightarrow x=-1\)
c) \(\frac{x}{14}=\frac{6}{y}=\frac{-15}{35}\)
\(\Rightarrow\left[\begin{matrix}\frac{x}{14}=\frac{-15}{35}\\\frac{6}{y}=\frac{-15}{35}\end{matrix}\right.\Rightarrow\left[\begin{matrix}x.35=-15.14\\6.35=-15.y\end{matrix}\right.\)
\(\Rightarrow\left[\begin{matrix}x=\frac{-15.14}{35}\\y=\frac{6.35}{-15}\end{matrix}\right.\Rightarrow\left[\begin{matrix}x=-6\\y=-14\end{matrix}\right.\)
Vậy \(x=-6;y=-14\)
HN
20 tháng 2 2017
a) \(\frac{-2x}{5}=-\frac{6}{3}\)
\(\Leftrightarrow-6x=-30\)
\(\Leftrightarrow x=5\)
b) \(\frac{x-2}{18}=-\frac{1}{6}\)
\(\Leftrightarrow-6\left(x-2\right)=-18\)
\(\Leftrightarrow x-2=3\)
\(\Leftrightarrow x=5\)
c) \(\frac{x}{14}=\frac{6}{y}=-\frac{15}{35}\)
\(\Leftrightarrow\frac{x}{14}=\frac{6}{y}=-\frac{3}{7}\)
\(\Leftrightarrow\left\{\begin{matrix}x=-6\\y=-14\end{matrix}\right.\)
12 tháng 2 2020
a) x - 13+x = -24-7 + x
2x-13 = -31 +x
2x-x = -31+13
x = -18
b) 12.20 = 15x
240 = 15x
x = 16
c) 42(-5) = 14x
-210 = 14x
x = -15
GH
19 tháng 2 2018
a) \(\dfrac{x-2}{15}=\dfrac{9}{5}\)
\(\Leftrightarrow x-2=\dfrac{9\times15}{5}\)
\(\Leftrightarrow x-2=27\)
\(\Leftrightarrow x=29\)
Vậy ...............
b) \(\dfrac{2-x}{16}=\dfrac{-4}{x-2}\)
\(\Leftrightarrow\dfrac{2-x}{16}=\dfrac{4}{2-x}\)
\(\Leftrightarrow\left(2-x\right)^2=64\)
\(\Leftrightarrow\left(2-x\right)^2-64=0\)
\(\Leftrightarrow\left(2-x\right)^2-8^2=0\)
\(\Leftrightarrow\left(2-x-8\right)\left(2-x+8\right)=0\)
\(\Leftrightarrow\left(-x-6\right)\left(-x+6\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}-x-6=0\\-x+6=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-6\\x=6\end{matrix}\right.\)
Vậy ..............
c) \(\dfrac{14}{x}=\dfrac{x-1}{4}\)
\(\Leftrightarrow x\left(x-1\right)=56\)
\(\Leftrightarrow x^2-x-56=0\)
\(\Leftrightarrow x^2+7x-8x-56=0\)
\(\Leftrightarrow x\left(x+7\right)-8\left(x+7\right)=0\)
\(\Leftrightarrow\left(x+7\right)\left(x-8\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x+7=0\\x-8=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-7\\x=8\end{matrix}\right.\)
Vậy ....................
19 tháng 2 2018
a) Ta có: \(\frac{x-2}{15}=\frac{9}{5}\Rightarrow5.\left(x-2\right)=9.15\)
\(\Rightarrow5x-10=135\)
\(\Rightarrow5x=145\)
\(\Rightarrow x=29\)
b) \(\frac{2-x}{16}=\frac{-4}{x-2}\Rightarrow\left(2-x\right).\left(x-2\right)=\left(-4\right).16\)
\(\Rightarrow4x-x^2-4=-64\)
\(\Rightarrow4x-x^2=-60\)
Lập bảng rồi tính ra
c) \(\frac{14}{x}=\frac{x-1}{4}\Rightarrow x.\left(x-1\right)=14.4\)
\(\Rightarrow x.\left(x-1\right)=56\)
Vì 56 = 8 x 7
\(\Rightarrow x=8\)
19 tháng 2 2018
Câu c) còn có thêm \(x=-7\) nữa nha MMS_Hồ Khánh Châu vì \(x\inℤ\) mà :')
R
23 tháng 6 2020
Bài 1:
a) \(\frac{25}{4}+\frac{-5}{4}=\frac{25-5}{4}=\frac{20}{4}=5\)
b)\(\frac{-5}{9}+\left(\frac{-2}{7}\right)=\frac{-35}{63}+\left(\frac{-18}{63}\right)=\frac{-53}{63}\)
c) \(\frac{1}{4}+\frac{9}{11}+\frac{7}{4}+\left(\frac{-2}{11}\right)=\left(\frac{1}{4}+\frac{7}{4}\right)+\left(\frac{-2}{11}+\frac{9}{11}\right)=2+\frac{7}{11}=\frac{22+7}{11}=\frac{29}{11}\)
d) \(\frac{-5}{19}.\frac{8}{19}+\left(\frac{-14}{19}\right).\frac{11}{19}=\frac{-40}{361}-\frac{151}{361}=-\frac{191}{361}\)
R
23 tháng 6 2020
Bài 2:
a) \(x+\frac{5}{9}=\frac{-8}{9}\) \(\Leftrightarrow x=\frac{-8}{9}-\frac{5}{9}\) \(\Leftrightarrow x=-\frac{13}{9}\)
b) \(\frac{-1}{8}-x=\frac{9}{20}\) \(\Leftrightarrow x=\frac{-1}{8}-\frac{9}{20}\) \(\Leftrightarrow x=\frac{-5}{40}-\frac{18}{40}\) \(\Leftrightarrow x=-\frac{23}{40}\)
c) (x + 5)3 - 12 = 15
\(\Leftrightarrow\)(x + 5)3 = 27
\(\Leftrightarrow\)x + 5 = 3
\(\Leftrightarrow\)x = -2
d) \(\left|x-3\right|-\frac{4}{15}=\frac{26}{15}\) \(\Leftrightarrow\left|x-3\right|=2\) \(\Leftrightarrow\orbr{\begin{cases}x-3=2\\x-3=-2\end{cases}}\) \(\Leftrightarrow\orbr{\begin{cases}x=5\\x=1\end{cases}}\)
22 tháng 4 2020
\(a/\frac{7}{9}-\frac{x}{3}=\frac{1}{9}\)
\(\Rightarrow\frac{x}{3}=\frac{7}{9}-\frac{1}{9}\)
\(\Rightarrow\frac{x}{3}=\frac{2}{3}\)
\(\Rightarrow x=2\)
Vậy \(x=2\)
\(b/\frac{1}{x}-\frac{-2}{15}=\frac{7}{15}\)
\(\Rightarrow\frac{1}{x}=\frac{7}{15}+\frac{-2}{15}\)
\(\Rightarrow\frac{1}{x}=\frac{1}{3}\)
\(\Rightarrow x=3\)
Vậy \(x=3\)
\(c/\frac{-11}{14}-\frac{-4}{x}=\frac{-3}{14}\)
\(\Rightarrow\frac{-4}{x}=\frac{-11}{14}-\frac{-3}{14}\)
\(\Rightarrow\frac{-4}{x}=\frac{-4}{7}\)
\(\Rightarrow x=7\)
Vậy \(x=7\)
\(d/\frac{x}{21}-\frac{2}{3}=\frac{5}{21}\)
\(\Rightarrow\frac{x}{21}=\frac{5}{21}+\frac{2}{3}\)
\(\Rightarrow\frac{x}{21}=\frac{19}{21}\)
\(\Rightarrow x=19\)
Vậy \(x=19\)
#Mạt Mạt#
mình đang cần gấp
\(-\frac{5}{x}=-\frac{15}{x-14}\)
\(\Rightarrow\frac{-15}{3x}=\frac{-15}{x-14}\)
\(\Rightarrow3x=x-14\)
\(\Rightarrow-2x=14\)
\(\Rightarrow x=-7\)
Vậy \(x=-7\)