1.47:
a) Ta có: \(\dfrac{3}{7}x-\dfrac{2}{5}x=-\dfrac{17}{35}\)
\(\Leftrightarrow\dfrac{1}{35}x=\dfrac{-17}{35}\)
hay x=-17
Vậy: x=-17
b) Ta có: \(\left(\dfrac{3}{4}x-\dfrac{9}{16}\right)\left(\dfrac{1}{3}+\dfrac{-3}{5}:x\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}\dfrac{3}{4}x-\dfrac{9}{16}=0\\\dfrac{1}{3}+\dfrac{-3}{5}:x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}\dfrac{3}{4}x=\dfrac{9}{16}\\\dfrac{-3}{5}:x=\dfrac{-1}{3}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{9}{16}:\dfrac{3}{4}=\dfrac{9}{16}\cdot\dfrac{4}{3}=\dfrac{36}{48}=\dfrac{3}{4}\\x=\dfrac{-3}{5}:\dfrac{-1}{3}=\dfrac{-3}{5}\cdot\dfrac{-3}{1}=\dfrac{9}{5}\end{matrix}\right.\)
Bài 1.48:
a) Ta có: \(\left(x-\dfrac{1}{3}\right)\left(x+\dfrac{2}{5}\right)>0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-\dfrac{1}{3}>0\\x+\dfrac{2}{5}< 0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x>\dfrac{1}{3}\\x< \dfrac{-2}{5}\end{matrix}\right.\)
b) Ta có: \(\left(x+\dfrac{3}{5}\right)\left(x+1\right)< 0\)
\(\Leftrightarrow\left\{{}\begin{matrix}x+1>0\\x+\dfrac{3}{5}< 0\end{matrix}\right.\Leftrightarrow-1< x< \dfrac{-3}{5}\)
các bạn giúp mik giải đề cương vs nha . mong sự giúp đỡ của các bạn . bài nào bạn biết làm cx đ ko cần làm hết