a: ĐKXĐ: \(x\notin\left\{1;-1;-\dfrac{1}{3}\right\}\)
a) ĐKXĐ: \(x\ne\pm1,x\ne-\dfrac{1}{3}\)
\(A=\dfrac{2x\left(x-1\right)-4\left(x+1\right)-2x^2+9x-3}{\left(x-1\right)\left(x+1\right)}.\dfrac{\left(x-1\right)\left(x+1\right)}{3x+1}=\dfrac{3x-7}{3x+1}\)
b) \(\left|9x+1\right|=2\Rightarrow\left[{}\begin{matrix}9x+1=2\\9x+1=-2\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=\dfrac{1}{9}\left(tm\right)\\x=-\dfrac{1}{3}\left(ktm\right)\end{matrix}\right.\)
\(A=\dfrac{3x-7}{3x+1}=\dfrac{3.\dfrac{1}{9}-7}{3.\dfrac{1}{9}+1}=-5\)
\(a,ĐK:x\ne-\dfrac{1}{3};x\ne\pm1\\ A=\dfrac{2x^2-2x+4x+4-2x^2+9x-3}{\left(x-1\right)\left(x+1\right)}\cdot\dfrac{\left(x-1\right)\left(x+1\right)}{3x+1}\\ A=\dfrac{11x+1}{3x+1}\\ b,\left|9x+1\right|=2\Leftrightarrow\left[{}\begin{matrix}9x+1=2\\9x+1=-2\end{matrix}\right.\Leftrightarrow x=\dfrac{1}{9}\left(x\ne-\dfrac{1}{3}\right)\\ \Leftrightarrow A=\dfrac{11\cdot\dfrac{1}{9}+1}{3\cdot\dfrac{1}{9}+1}=\dfrac{20}{9}:\dfrac{4}{3}=5\)
