Bài 4:
a: \(\dfrac{5}{7}\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{4}{7}\right)+\left(\dfrac{1}{3}-\dfrac{1}{2}-\dfrac{4}{7}\right):\dfrac{7}{5}\)
\(=\dfrac{5}{7}\cdot\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{4}{7}\right)+\dfrac{5}{7}\left(\dfrac{1}{3}-\dfrac{1}{2}-\dfrac{4}{7}\right)\)
\(=\dfrac{5}{7}\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{4}{7}+\dfrac{1}{3}-\dfrac{1}{2}-\dfrac{4}{7}\right)\)
\(=\dfrac{5}{7}\cdot0=0\)
b: \(\dfrac{5}{7}:\left(\dfrac{15}{8}-\dfrac{1}{4}\right)-\dfrac{5}{7}:\left(\dfrac{1}{4}+\dfrac{1}{2}\right)\)
\(=\dfrac{5}{7}:\dfrac{15-2}{8}-\dfrac{5}{7}:\dfrac{1+2}{4}\)
\(=\dfrac{5}{7}\cdot\dfrac{8}{13}-\dfrac{5}{7}\cdot\dfrac{4}{3}\)
\(=\dfrac{5}{7}\left(\dfrac{8}{13}-\dfrac{4}{3}\right)=\dfrac{5}{7}\cdot\dfrac{24-52}{39}\)
\(=\dfrac{5}{7}\cdot\dfrac{-28}{39}=\dfrac{-28}{7}\cdot\dfrac{5}{39}=-\dfrac{20}{39}\)
Bài 1
d: \(\left(x+1\right)^2-120=1\)
=>\(\left(x+1\right)^2=121\)
=>\(\left[{}\begin{matrix}x+1=11\\x+1=-11\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=10\\x=-12\end{matrix}\right.\)
