a: x+1/4=-7/2
=>x=-7/2-1/4=-14/4-1/4=-15/4
b: =>2/3:x=-7-1/3=-22/3
=>x=-2/3:22/3=-2/3*3/22=-1/11
d: =>x-(25/20-28/20)=9/20
=>x+3/20=9/20
=>x=6/20=3/10
e: =>(3x-2/5)^2=9/25
=>3x-2/5=3/5 hoặc 3x-2/5=-3/5
=>3x=1 hoặc 3x=-1/5
=>x=1/3 hoặc x=-1/15
\(a,\dfrac{1}{4}+x=-\dfrac{7}{2}\)
\(x=-\dfrac{7}{2}-\dfrac{1}{4}\)
\(x=-\dfrac{14}{4}-\dfrac{1}{4}=-\dfrac{15}{4}\)
\(b,\dfrac{1}{3}+\dfrac{2}{3}:x=-7\)
\(\dfrac{2}{3}:x=-7-\dfrac{1}{3}\)
\(\dfrac{2}{3}:x=-\dfrac{21}{3}-\dfrac{1}{3}\)
\(\dfrac{2}{3}:x=-\dfrac{22}{3}\)
\(x=\dfrac{2}{3}:\dfrac{-22}{3}=-\dfrac{1}{11}\)
\(d,x-\left(\dfrac{5}{4}-\dfrac{7}{5}\right)=\dfrac{9}{20}\)
\(x-\dfrac{-3}{20}=\dfrac{9}{20}\)
\(x=\dfrac{9}{20}+\dfrac{-3}{20}=\dfrac{3}{10}\)
\(e,\left(\dfrac{2}{5}-3x\right)^2=\dfrac{9}{25}\)
\(\Leftrightarrow\left[{}\begin{matrix}\dfrac{2}{5}-3x=\dfrac{3}{5}\\\dfrac{2}{5}-3x=-\dfrac{3}{5}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}3x=-\dfrac{1}{5}\\3x=1\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{1}{15}\\x=\dfrac{1}{3}\end{matrix}\right.\)
