D

D

`0,75-43/80:(-4/5+2,5*3/4)`

`=0,75-43/80:(-4/5+15/8)`

`=0,75-43/80:43/40`

`=3/4-1/2`

`=1/4`

  0,75 - \(\dfrac{43}{80}\) : ( -  \(\dfrac{4}{5}\) + 2,5 \(\times\) \(\dfrac{3}{4}\))

= 0,75 - \(\dfrac{43}{80}\) : ( - \(\dfrac{4}{5}\) +  \(\dfrac{15}{8}\))

= 0,75 - \(\dfrac{43}{80}\) : \(\dfrac{43}{40}\)

= 0,75 - \(\dfrac{1}{2}\)

= 0,75 - 0,5

= 0,25 

1 19/60

1/5 +1 - 0,75/2,5+ 5/3 - 1,25 

\(=1\frac{19}{60}\)

79/60

\(a,\left[0,75x+\frac{5}{2}\right]-\frac{4}{7}-\left[-\frac{1}{3}\right]=-\frac{5}{6}\)

\(\Leftrightarrow\left[0,75x+\frac{5}{2}\right]-\frac{4}{7}+\frac{1}{3}=-\frac{5}{6}\)

\(\Leftrightarrow\left[0,75x+\frac{5}{2}\right]=-\frac{5}{6}-\frac{1}{3}+\frac{4}{7}\)

\(\Leftrightarrow0,75x+\frac{5}{2}=-\frac{25}{42}\)

\(\Leftrightarrow0,75x=-\frac{65}{21}\Leftrightarrow x=-\frac{260}{63}\)

\(b,\left[4x-9\right]\left[2,5+-\frac{7}{3}x\right]=0\)

\(\Leftrightarrow\orbr{\begin{cases}4x-9=0\\2,5+-\frac{7}{3}x=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{9}{4}\\x=\frac{15}{14}\end{cases}}\)

Vậy \(x\in\left\{\frac{9}{4};\frac{15}{14}\right\}\)

Tham khảo nhé phamthiminhanh

a) \(\left(0,75x+\frac{5}{2}\right)-\frac{4}{7}-\left(-\frac{1}{3}\right)=-\frac{5}{6}\)

=>   \(0,75x+\frac{5}{2}-\frac{4}{7}+\frac{1}{3}=-\frac{5}{6}\)

=> \(0,75x=-\frac{5}{6}-\frac{5}{2}+\frac{4}{7}-\frac{1}{3}\)

=>  \(0,75x=-\frac{65}{21}\)

=>   \(x=-\frac{260}{63}\)

b) \(\left(4x-9\right)\left(2,5+-\frac{7}{3}x\right)=0\)

=>   \(10x-\frac{28}{3}x^2-22,5+21x=0\)

=>   \(-\frac{28}{3}x^2+31x-22,5=0\)

=>   Phần còn lại bạn tự giải tiếp nhé!

\(\frac{0,375-0,3+\frac{3}{11}+\frac{3}{12}}{-0,625+0,5-\frac{5}{11}-\frac{5}{12}}+\frac{1,5+1-0,75}{2,5+\frac{5}{3}-\frac{5}{4}}\)

\(=\frac{3\left(0,125-0,1+\frac{1}{11}+\frac{1}{12}\right)}{-5\left(0,125-0,1+\frac{1}{11}+\frac{1}{12}\right)}+\frac{3\left(0,5+\frac{1}{3}-\frac{1}{4}\right)}{5\left(0,5+\frac{1}{3}-\frac{1}{4}\right)}\)

\(=\frac{-3}{5}+\frac{3}{5}=0\)

a, \(\left|x\right|+0,75=2\Rightarrow\left|x\right|=1,25\Rightarrow x=\pm1,25\)

b, \(\left|x+\dfrac{1}{3}\right|-4=1\Rightarrow\left|x+\dfrac{1}{3}\right|=5\Rightarrow\left|x\right|=\dfrac{14}{3}\Rightarrow x=\pm\dfrac{14}{3}\)

c,

\(\left|x\right|+2,5=0\Rightarrow\left|x\right|=-0,25\) (vô lí)

Vì \(\left|x\right|\ge0\) => x vô nghiệm

a) \(\left|x\right|+0,75=2\)

\(\Leftrightarrow\left|x\right|=2-0,75=1,25\)

\(\Rightarrow\left[{}\begin{matrix}x=-1,25\\x=1,25\end{matrix}\right.\)

b) \(\left|x+\dfrac{1}{3}\right|-4=1\)

\(\Leftrightarrow\left|x+\dfrac{1}{3}\right|=1+4=5\)

\(\Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{3}=5\\x+\dfrac{1}{3}=-5\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{14}{3}\\x=-\dfrac{16}{3}\end{matrix}\right.\)

c) \(\left|x\right|+2,5=0\)

\(\Leftrightarrow\left|x\right|=0-2,5=-2,5\)

Vì \(\left|x\right|\ge0\) mà \(-2,5< 0\) nên \(x\in\varnothing\)

\(=\frac{3}{4}-\frac{43}{80}:\left(\frac{-4}{5}+\frac{5}{2}.\frac{3}{4}\right)\)

\(=\frac{3}{4}-\frac{43}{80}:\left(\frac{-4}{5}+\frac{15}{8}\right)\)

\(=\frac{3}{4}-\frac{43}{80}:\frac{43}{40}\)

\(=\frac{4}{3}-\frac{1}{2}=\frac{5}{6}\)

\(a)\frac{9}{4}\times y=\left[\frac{5}{7}-\frac{3}{14}\right]\times\frac{4}{7}\)

\(\Rightarrow\frac{9}{4}\times y=\left[\frac{10}{14}-\frac{3}{14}\right]\times\frac{4}{7}\)

\(\Rightarrow\frac{9}{4}\times y=\frac{1}{2}\times\frac{4}{7}\)

\(\Rightarrow\frac{9}{4}\times y=\frac{2}{7}\)

\(\Rightarrow y=\frac{2}{7}:\frac{9}{4}=\frac{8}{63}\)

b, Tương tự câu a