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a. -3/4 x 12/-5 x (-25/6)=-15/2
b. -2 x -38/21 x -7/4 x (-3/8)=-19/8
c. (11/12: 33/16) x 3/5=4/15
d. 7/23 x [(-8/6)- 45/18]=-7/6
Bài 1:
a) \(=\dfrac{8}{15}\left(\dfrac{7}{13}+\dfrac{6}{13}\right)=\dfrac{8}{15}.1=\dfrac{8}{15}\)
b) \(=\dfrac{3.3-7-2.4}{12}=-\dfrac{6}{12}=-\dfrac{1}{2}\)
Bài 2:
\(\dfrac{x}{2,7}=-\dfrac{2}{3,6}\Rightarrow x=\dfrac{\left(-2\right).2,7}{3,6}\Rightarrow x=-\dfrac{3}{2}\)
Bài 3:
\(\dfrac{x}{2}=\dfrac{y}{5}=\dfrac{x+y}{2+5}=-\dfrac{21}{7}=-3\)
\(\Rightarrow\left\{{}\begin{matrix}x=\left(-3\right).2=-6\\y=\left(-3\right).5=-10\end{matrix}\right.\)
\(2x-15=21\Rightarrow2x=36\Rightarrow x=18\)
\(2\left|x+2\right|+7=25\Rightarrow2\left|x+2\right|=18\Rightarrow\left|x+2\right|=9\)
\(\Rightarrow\left[{}\begin{matrix}x+2=9\Rightarrow x=7\\x+2=-9\Rightarrow x=-11\end{matrix}\right.\)
\(3x+12=2x-4\)
\(\Rightarrow3x=2x-16\Rightarrow-x=16\Rightarrow x=-16\)
\(\left|2x-5\right|=1\)
\(\Rightarrow\left[{}\begin{matrix}2x-5=1\Rightarrow2x=6\Rightarrow x=3\\2x-5=-1\Rightarrow2x=4\Rightarrow x=2\end{matrix}\right.\)
\(2\left|x-5\right|+3=4\Rightarrow2\left|x-5\right|=1\Rightarrow\left|x-5\right|=0,5\)
\(\Rightarrow\left[{}\begin{matrix}x-5=0,5\Rightarrow x=5,5\\x-5=-0,5\Rightarrow x=4,5\end{matrix}\right.\)
a. \(2x-15=21\\ \Leftrightarrow2x=36\\ \Leftrightarrow x=18\)
c. \(3x+12=2x-4\Leftrightarrow x=-16\\ \)
a)\(-\frac{2}{7}x\frac{21}{8}=\frac{-2x3x7}{7x4x2}=-\frac{3}{4}\)
b) 0,24 x -15/4=-9/10
c) (-2) x (-7/12)=7/6
d) (-32/25) : 6=-16/75
\(a.\frac{-2}{7}\times\frac{21}{8}=\frac{\left(-2\right)\times21}{7\times8}=\frac{-1\times3}{1\times4}=\frac{-3}{4}.\)
\(b.0,24\times\frac{-15}{4}=\frac{6}{25}\times\frac{\left(-15\right)}{4}=\frac{6\times\left(-15\right)}{25\times4}=\frac{3\times\left(-3\right)}{5\times2}=\frac{-9}{10}\)
\(c.\left(-2\right)\times\frac{\left(-7\right)}{12}=\frac{\left(-2\right)\times\left(-7\right)}{12}=\frac{14}{12}=\frac{7}{6}\)
\(d.\frac{-32}{25}:6=\frac{-32}{25}\times\frac{1}{6}=\frac{-16}{75}\)